Of course, the biggest risk is probably Wandering Monsters. One of the problems with 3E & 4E is not so much that you can't introduce wandering monsters, but that they can upset a dungeon carefully balanced for the PCs leveling at a particular point.
The problem here, imho, is the assumption that the pcs can be led by the nose through a certain sequence of encounters, yielding a certain number of xp, in a predictable fashion.
Is it a problem when the party leaves the dungeon and goes to take care of that local thief who has been aggravating them since level 1? Should the dm not reward xp for engaging with the campaign in preference to keeping an artificial pace? What if the pcs find the secret back entrance that takes them to the lower levels of the dungeon first? Oh noes, my artificial pacing is off!
If XP wasn't done on a per monster basis, but instead at reaching certain "points" along the adventure, this wouldn't be as much a problem (though treasure still might).
Some dms do award xp that way, or simply tell the party when to level. Which is fine if that's the style you want- but in that case, xps are extraneous to the discussion.
Also, if the DM were given options to restock/resupply the bad guys when PCs rest, this could also be a balancing factor. If this options are presented at the start of the adventure for the DM, or presented and discussed in the DMG, it would become a balancing factor.
Some examples:
1) One or more rooms occupants are restocked with reinforcements
2) The complex goes on alert; chances of surprise are lowered and NPCs are prebuffed in preparation for the PCs
3) The bad guys call in some heavy artillery or the clearing of an area allows a more powerful monster to move in
4) Time closes in on preparations the bad guys have made, possibly making them stronger
5) Traps, barriers or other obstacles have been put in place to impede the character's progess
All great ideas.
But to all those people who have suggested that the problem is solved by wandering monsters and threat escalation--well, that's also a solution that sacrifices story concerns for the sake of game rules and game balance.
This is a game we're talking about. The story is what you tell about how the pcs interacted with the adventure. I'll suggest (my playstyle preferences are showing here!) that if you have to have a certain pace in your story, you're best off writing a book and not running a game.
Even so, the suggestion that the organized inhabitants of a dungeon won't proactively seek out the guys who have been killing their friends for the past three days also sacrifices "story concerns" (which I would term "verisimilitude" in this case) for the sake of some spectral idea of fairness/taking it easy on the players/not being mean/let's not mess up the "story" that inevitably has the bad guy encountered in the same room, no matter the time of day or night or what has happened in the interim.
And unlike the "rest area" idea, most of the "punish the players ideas" are huge time sinks. Wandering monsters and re-filled rooms are just extra combats that do nothing to advance progress through the adventure. They're rarely interesting fights: The wandering monster is off a table and the resting party chooses the terrain, making it hard for the GM to prep for an interesting encounter, whereas the re-stocked room is repetitive: similar creatures re-fill the exact same combat spaces. And there can't be much that makes them interesting from a plot perspective, because they're likely to not happen in the first place.
Again there's a lot of reference to plot, progress, etc. The problem with story-based games is keeping the story flowing, and if that's your main problem, maybe the campsites idea is right for you. Personally, I find that the flow of the story of my games comes
after they are played, and the pcs drive that flow in the game. They aren't 2nd level by the time they find the stairs down? Well, that's okay; either they'll get greater dangers and treasures for heading down or they'll do something else. They reach 2nd level well before they find those stairs? That's okay too.
Beyond that, wandering monsters certainly can make for interesting combats, as well as be interesting from a "plot" perspective. I'll give you an example. The party imc had a wandering encounter with a group of yuan-ti cultists. Several games later, they learned about a group of yuan-ti in a nearby swamp. Lo and behold, the random encounter led to a cool adventure in a half-sunken yuan-ti ziggurat! Random encounters aren't just monsters that wander the world looking to attack pcs; they are creatures with their own goals too. When the players ask, "Why are these guys here?", a good dm will come up with an answer, even if the players don't know what it is.
I'm not trying to say that wandering monsters are bad. In many cases, they can be great (I'm using them in my current campaign, in fact). My point is that they're a tool that makes more sense in some stories than in others--and that relying on the threat of wandering monsters as the primary enforcer of longer adventuring days requires GMs to either constrain themselves to certain types of stories or to use wandering monsters in situations where they don't make sense.
Oh, absolutely. I'll add that wandering monsters make a lot more sense if the dm thinks about what to put on his wandering monster charts and why they are on it. A long-lost desert tomb shouldn't have a dire boar on the table, but a gray ooze or handful of skeletons make perfect sense. The social adventure where the pcs need to slip away from a dinner party and search the host's office in secret shouldn't have ghouls and giants, it should have the house dog and servants. Using "just any ol' chart" to generate wandering monsters IS a huge problem if you want to maintain verisimilitude.
