Ruin Explorer
Legend
That's true in more symmetrical games, but D&D is profoundly asymmetrical.It is all fun and games until the DM can do it back to you.
Makes my players think a bit on how the rules should be interpreted.
It's bit like the old "We only have to be lucky once, you have to be lucky every time" deal.
The players have to win (almost) every battle if they expect to be alive, and have to shepherd their resources with care (assuming an attrition-heavy game).
Monsters and NPCs don't have a single care in the world and can blow absolutely every resource they have at the maximum possible rate for the one combat 99.9% of them are in. Any monster that can cast two fireballs/round is probably casting two fireballs per round every single round it's alive, if it can. They're always going flat out, because there's literally no reason not to. This is why a lot of monster abilities have things like dice-based refresh rolls rather than "X per day", and if you follow 5E's monster design you can see how that's only becoming more the case. To put it another day, to monsters and NPCs, every day is the legendary "5 minute work day".
It's a completely different game for each side. Furthermore, the monsters, particularly in 4E and 5E, are absolutely designed on this basis - i.e. that they're going to go absolutely flat out and blow everything they have, as fast as they can, in combat. If you play them any other way, they'll be less effective than designed - drastically so in some cases (which of course can be intentional on your part, but still).
There are very few rules which impact players and monsters equally, and this rule 100% is not one of them, because decreasingly few monsters (and it's going to drop sharply again after MM 2024, we know) even use "spells" - instead they largely use uniquely designed abilities which may be similar to spells, but aren't, and aren't limited in the same.