Because my players' suspension of disbelief began to suffer when exploring more "normal" dungeons, I have created some big dungeons which are based on bigger,
realistic structures: castles, towns, military structures, bunkers, etc.
However, another problem has come up. A structure which is able to hold a regiment contains many repetitions: kitchen, bathroom, sleeping room, again and again, because a place where people live is more utilitarian than most fantasy dungeon designs.
Now my group isn't suffering a lack of suspension of disbelief, but I suspect they are a bit overwhelmed: their normal routine of sifting through every room is not possible anymore, and they get restless. I suspect they fear losing out on interesting information now that the dungeon isn't linear.
I am not sure how to keep the players busy and focused in a dungeon that has many equal rooms. How can I GM these larger structures without the players becoming frustrated in this way?
Some information about the current background. The group explores the structure with a map which is under a glass plate covered by rice (sand is leaking too much for my taste). The advantage is that I do not need to describe every room and they can make maps (naturally I have the master map with undiscovered features like traps, hidden rooms etc.), the disadvantage is that they realize how vast the structure is and that I gave them the freedom to explore.
The structure itself has a very specific and very important purpose which is the reason why it is so vast, the constructors had no choice. The reason was temporary, so the inhabitants left bit by bit. The inhabitants and their reason to live there changed rooms and build hidden ones without never finding all rooms of their predecessors. So the current explorers (my group) find plundered and vandalized old rooms and sometimes an older trap which is not working anymore. But the last sessions they found out that someone left fresh traps and a message that their presence is not welcome >:)
Best Answer
The main trick is to not have the players feel like they have to obsessively search every part of every room.
Over time, this is dictated by your actions as the GM. (Obviously there's some switchover time if you're shifting styles.) If you hide a critical clue or tasty treasure requiring a DC 20 Perception check under the bunk of barracks room #57/100, or put a deadly trap on door #23/50, they're either going to have to search everything or just throw up their hands and say "screw it, we'll bull forward and maybe we're missing something."
You don't mention a game system, though you should because different games approach this problem differently.
GUMSHOE would say "Don't require search checks to find important things. PCs find them automatically. Require checks after that to interpret what was found or whatever, but if your game would be blocked by a roll, don't make the roll in the first place." This obviates the problem.
A D&D 3e answer might be "pre-roll a bunch of player perception checks ahead of time, don't make them say it and roll it but just apply those checks whenever they go into a new area, if their stated SOP is to search around everywhere." This doesn't remove the problem, but it speeds it up significantly. Similar is just when they say "we search barracks #57" - if they have the time to take 20, you don't have to roll, just spend some in-game time (not table time) and tell them what they find (take 10 and take 20 reduce resolution time). Or you can just cut to the chase and come right out and say "there's nothing new here."
A drama-game (or even D&D 4e I think) type answer would be to say out loud to them "Hey guys, important stuff will never be in some generic room, I'm only going to put important information into clearly 'named' rooms, just like only 'named' NPCs are important." This removes the issue at a metagaming level, though at great cost to simulation.
4e and 5e have "passive perception" in an attempt to speed up the game, but your issue is that they want to actively search and not just take the passive chance, so that doesn't help much.