One of the things that plagues some D&D games (my own included, on occasion) is what is known as “the fifteen minute workday problem”. To wit, characters in a dungeon go through two or three rooms, find themselves down some hit points and/or spells, and then return to the surface, heal up and re-memorize spells to return on the next day. Or, alternatively, they barricade themselves in a room and camp out in the dungeon itself. It’s a problem that especially presents itself in lower-level games, because the spell casters have few spells and must recharge more often.
There are some tricks a game master can employ in order to discourage this behavior. Locking the player characters in the dungeon (whether literally or by simply denying them egress through having them get lost, having monsters block the exit, etc.), disrupting spell-casters’ rest with random encounters, etc. But it’s very easy to overdo these sorts of things, however, and can begin to smack of “the DM is just going to punish us for leaving, so we might as well keep going until we’re dead” in the minds of the players.
4E attempted to address this problem at least in theory with its classification of powers as being per-encounter, per-day, etc. To my mind, however, that was a bit too “gamey”, and lacked any sort of real in-game justification. But the problem is certainly not unique to 4E; it’s existed since the beginning of the game.
I wonder, though, if there is some way of addressing this issue in a way that doesn’t offend my grognardly sensibilities? On the one hand, part of the whole aesthetic of an old-school game is resource management. It’s not just about making the right tactical choices in a combat, but making the right operational choices when selecting spells and buying equipment. In once sense, the megadungeon is its own solution to the problem; if the game master doesn’t slack off when it comes to rolling for random encounters, the mere fact that the player characters may well need to fight their way out will encourage them to stay in longer. But that just shifts the site of rest to a barricaded room inside the dungeon, rather than the local inn or convenient cave near the site of the dungeon.
There is one solution to the problem, which applies perhaps more to the megadungeon environment than a smaller encounter area, but I’m sure the principle could be applied.
The monsters get tougher (or, perhaps, more wary) if the player characters keep coming in and doing hit-and-run sortees.
Not in the sense that they somehow get bonuses to hit, or more hit dice, but in the sense that they become more organized. They’re more on their guard. Patrols are more frequent. Rooms and corridors are restocked with guards, ready to send out messengers to alert the leader to the renewed presence of the intruders. Once the player characters clue into the fact that the monsters will be waiting for them (perhaps even with traps, ambuscades, tougher monsters from deeper within the dungeon who are brought up as reinforcements, etc.), they may decide that two-rooms-a-day is not the best way to go. Maintaining the momentum, and thereby the element of surprise, becomes a superior (and thus preferable) strategy.
Naturally, this doesn’t mean that resistance can’t stiffen during the player characters’ foray. Just because they haven’t returned to the surface doesn’t mean that the orcs will automatically stay in their rooms, conveniently grouped in 3’s and 4’s, perfect for slaughter and easy x.p. But that should be a more “ad hoc” thing on the part of the defenders (except for those very lawful humanoid tribes that have contingency plans already in place, complete with pole-arm-wielding troops to command narrow corridors and such), and to be expected. The idea is that pressing on should be the preferable option to retreat, except when the resources of the party really are exhausted, and R&R becomes required.