Not at all. Because if the party has a healer, 99% of the time that healer is also a spellcaster, because Mearls & co. danced on the Warlord's grave. Meaning the party has every reason to stop fighting once the spell slots run out and they're functionally out of resources to prevent catastrophic failure.
We don't need casters to heal. Healing is still something we do when things go wrong, but we have hit die healing, potions as basic equipment, various class abilities, and various sources of temporary hit points.
These things generally provide more hit points than a few spells.
It's not about ignoring the 24-hour cycle. It's about packing it in. Waiting for a new day rather than taking on new challenges when the biggest resources are already used up...most importantly the healing resources, which are the ones the martial characters need the most because they're in the line of fire for the nastiest attacks.
That's only true if the players built their martials and play in a style that causes them to be dependent on magical healing.
Barbarians, fighters, and rogues all get weapon mastery. These are decent options that don't require resting or resources, and these are used to attack with advantage to drop monsters faster, be attacked with disadvantage to leverage the better armor and hit points more, and restrict movement to avoid getting attacked at all.
Things like Menacing Attack, which can be done with a ranged weapon, can keep strong opponents from closing to inflict damage when we look at resource abilities, and that renews on a short rest.
Hit die healing on short rests is a lot of healing. All martial characters can buy and carry as many healing potions as shops (ie the DM) will allow, but if that availability becomes a concern any martial character can learn to brew their own healing potions for half the cost too.
All fighters have second wind for healing. Fighters have two to four of these plus recover one each short rest, and on the premise of being able to take many short rests instead of waiting out the day to take one long rest it becomes easy to three or more additional second winds over that two to four base. At 10th level using second wind seven times is over 100 hp worth of healing.
Rally gives temp hit points, and with Relentless it can be done ad nauseam at high levels. Bait and Switch increases AC, Parry reduces damage, Disarming Attack takes weapons away so they cannot be used to attack, Evasive Footwork also adds AC, and more options in those maneuvers on a short rest recovery. Battle masters have plenty of options to mitigate damage.
Psi Warriors have Protective Field to reduce damage.
Champions lack those earlier options available to Battle Masters and Psi Warriors but advantage on initiative helps, Heroic Warrior is excellent, and later on Survivor is also excellent because of Heroic Rally.
All rogues have Uncanny Dodge and Evasion to mitigate damage. These can be done a lot. Cunning Action also make rogues hard to pin down. Cunning Strike, Improved Cunning Strike, and Devious Strikes provide options in addition to Weapon Mastery. It doesn't cost a rogue a spell slot to use Devious Strikes for Knock Out. These options neither require a long rest nor a short rest.
Rogue subclass abilities don't add much, but a Thief with Fast Hands and Use Magic Device helps. Keep in mind that 1st level spell scrolls are also basic equipment now, and a Thief proficiency in Arcana will auto-succeed on the check using 4th level spell scrolls or lower because of Reliable Talent without any investment in INT or applying expertise.
All barbarians have damage reduction from Rage, and Rage also recovers a use on short rests. Barbarians as a class don't gain a lot of healing, but they do have the best hit die for healing, and Danger Sense and Feral Instinct help. Barbarians also have Brutal Strike and Improved Brutal Strike on top of Weapon Mastery similar to rogues and Cunning Strike.
Wild Heart gives choices of abilities from Rage of the Wilds and Power of the Wilds when Rage is activated so these are also short rest recovery abilities. Beast Sense, Speak with Animals, and Commune with Nature are all rituals granted to these barbarians so don't require finite resources like spell slots. World Tree gives Vitality of the Tree for a lot of temp hit points, and Battering Roots to increase Weapon Mastery options. These subclasses are both strong options to go without spell casters.
All monks have Patient Defense and Step of the Wind (and later Improved Patient Defense), Deflect Attacks, Stunning Strike, Evasion, Self-Restoration, and eventually Superior Defense. Focus Points are also a short rest recovery so they can do this a lot while the casters are waiting out the day so that they can long rest again.
Elemental and Shadow monks have magical abilities that aren't so defensive or healing but a party can work around using Darkness from Shadow Arts defensively. Open Hand monks add Weapon Mastery like abilities with Open Hand Technique and added mobility with Fleet Step, and some offensive power with Quivering Palm but also don't add short rest healing abilities.
Mercy monks, OTOH, add Hand of Healing and Physician's Touch using Focus Points for that short rest recovered healing on a martial class.
Related feats include: Healer, Lucky, Musician, Tough, Chef, Defensive Duelist, Durable, Heavy Armor Master, Inspiring Leader, Sentinel, Shield Master, Weapon Master, Interception, Protection, to cover abilities to mitigate damage.
The Chef feat is a suitable replacement for our lost Song of Rest, Inspiring Leader is every short rest, and Healer's Battle Medic increases the healing from hit dice to make them more effective when those are already a large source of healing.
The idea that the characters need to be built around and wait for spellcasters to heal them is an old school mentality that's a bit bonkers. WotC went a long way to take the healing onus off of those spellcasters so that they can use their spell slots on spells other than healing.
It's even more bonkers when a party can, instead of expecting all the PC's to cater to those spellcasters, take a warlock instead who's more than happy to play on the short rest model along with those martial characters in the event a spellcaster would come in handy. The need to take long rests for spellcasters is an outdated concept at this point.
Martial characters will eventually also need that long rest, but there is no need to pace it on a spellcaster's desire to blow their spell slots and then expect the game world to pause for them.
So are martials. That changes nothing.
Martials don't need to wait out the day just because spellcasters think they can and should be entitled to do so.
I can take a Battle Master fighter, Thief rogue, World Tree barbarian, and Mercy monk and we can keep going for a long time. You might not think that's perfect, but imperfect action is far more productive than inaction waiting for the perfect time.
The entire time those spell casters are waiting out the clock to recover spell slots is time they are doing nothing that the martial characters can continue doing damage until they also need to take that long rest, which isn't the same time spellcasters do just because those spellcasters blew all their slots.
Why not? It's amount of damage per day. Only one set of classes is dependent on having a bazillion combat rounds each day. The other can burn through all of their resources and then present a very strong argument that we will be stronger if we pack it in.
No, the spellcasters are dependent on the world pausing around them and pretending burst damage is consistent damage through the rest of the day. A lot of damage in a relatively short period of time is the opposite of consistent damage and doesn't become consistent damage by pretending that's taken place over the day.
"But it's damage per day" is mental gymnastics trying to justify everyone waiting with the spellcasters who are accomplishing nothing for long periods of time under that argument.
Great! You have groups intentionally playing suboptimally. That's totally fine. It's not what the game actually gives mechanical rewards to.
Except it's not suboptimal because we are accomplishing goals while resting to recover slots is accomplishing nothing in the same time frame. A group that does that repeatedly is going to fall behind farther and farther in accomplishing those goals.
My group will end up levels higher and more quests completed while your group under your model is still sleeping their time away. I suppose the troll stealing villagers also stops so your spellcasters can rest. That's not optimal.
I have personally seen it be a direct problem. Does that make you happy? To know that this is real, and you've just had a gentleperson's agreement not to let it be an issue?
I have players who play the game and DM's who run the campaign. What you're describing ignores the rest of the in-game world and expects players to cater to that.
If someone's wizard or cleric decides to not conserve and pace their spells the rest of the party shouldn't be expected to stop just for that wizard because we never needed them in the first place for us to play. We'll just keep playing and they can either play too but without all those spells, or go rest and watch us continue playing while they're doing nothing but resting and we're playing the game. They'll either quit the group or learn to keep to the group's pace. IME people don't quit groups and learn to pace to the group instead.
We finish the dungeon or that portion of the adventure because that's what the characters need to do as part of the adventure story. It's weird to me when a person's idea of roleplaying heroic adventure is to sleep as often as possible while waiting to sleep as often as possible instead of doing the things that progress the adventure.
If the goal is to rescue the farmer's daughter we're going to continue towards rescuing the farmer's daughter. We're not going to say to ourselves, "let's go take a nap, she'll probably be fine for another day..."
Concentration helps, but it should be far more widespread. There are far too many spells that should require it but don't. You are correct that 3.x/PF1e favored casters "a lot more", but that's kind of damning with faint praise. Because 3.x was so massively, horrifically broken, and nearly every possible mechanic favored spellcasters or punished martials or both.
To be better than literally the single worst D&D for martial/spellcaster balance isn't saying much!
I enjoyed 3.x, but it was definitely caster-centric. I had a regular group with a house rule that banned me from playing spellcasters claiming I was min/maxing over their characters, but I wasn't really. That's just how that system worked.
I find 5.24e is better for martials in the first and second tiers of play, and it's only when high level spells come into play that things start shifting the other way. I'd play a fighter or rogue over a wizard or cleric in the first five levels any day. Limited spell slots with low DC's and poor saving throws against concentration is kind of brutal for spellcasters at low levels.
Your solution to the limited spell slots is no limits on the resting, but it's a premise with which I can't agree because it's counter productive to accomplishing the goals of the adventure within a reasonable in-game time frame. It's gamist.
Six months is 26-27 weeks. Only requires that you get the first handful of levels rapid-fire, or start at a slightly higher level, to work out as about one level every other session. E.g. if you start at level 5, you'd only need back-to-back levelling twice in that six-month period. Of course, it could also be that they were slightly exaggerating in both directions, e.g. not quite 20 but maybe 18 or 19 and not a mere six months but seven or eight. Going from level ~4 to level ~18 in just over seven months is ~14 levels gained in ~31 weeks, or about 2.2 weeks per level (meaning, most of the time it's 2 weeks, but occasionally it's 3).
It's certainly fast, if ECMO3's group isn't starting at a higher level. But this just proves a point I've made many, many times on this forum and which people always deny, despite all evidence to the contrary: People presume absolutely every group starts at level 1 and never starts higher. Further, note the pace at which you say your levels come: closer to two years than one year. Call it 20 months, 86.96 weeks, call it 87 for simplicity. Given you have 19 levels to gain in that span (since you start at 1), that's more than four and a half weeks for each level, including level 2 and 3, which WotC has explicitly designed to take only one and two sessions apiece before settling at about 4 sessions apiece from there on out. And if we tweak it to assume you do get level 2 by the end of the first session and level 3 by the end of the third, that just makes all the others even slower, taking nearly five weeks every time (4.94).
And people say my experience of DMs dragging out the XP rate is somehow weird and divergent!
I prefer maintaining the levels for a bit of time to enjoy them. When the levels rush by I think takes away from experiencing the game at those levels.
Six months for me and I'm usually at about 9th-11th level.
Session based advancement is 2nd level after the first gaming session, 3rd level after the second gaming session, 4th level after two more gaming sessions, and an additional level after each two to three gaming sessions after that. That's assuming four hour gaming sessions each with appropriate XP. According to that guideline from the DMG weekly sessions would take a month to get to 4th level, and five months later a character would be about 12th level.
Under those guidelines it takes about eleven months to hit 20th level and leaves a month to play at that level so the full campaign would be about a year.
