Scott Christian
Hero
Good point; and after the first two or three rooms all being the same the players will most likely come up with some sort of quickie SOP for any further rooms that are similar. Frequent occurrence, too: many castles or dungeons or abbeys or such would have lots of small rooms for staff (or monks, in an abbey) and checking all those out can get tedious.
The concern is that if the DM batches and skips over those similar rooms too quickly she risks either a) telegraphing that there's nothing there or b) not giving the players a reasonable chance to find what is there e.g. the fourth room on the left has a secret door in the back wall leading to a passage...
Ten sessions is about our long-term average for a typical dungeon or adventure; slightly lower at low level and slightly higher at high.
I understand that missing something could be a concern. But in my experience, it never should be. Storytellers, for that is what DM's are, need to highlight, emphasize, foreshadow or imply the difference so players can know. The same way authors or directors choose to highlight a setting. In a scary movie, they use camera angles to make sure that creepy doll is in the frame. In action movies they make sure the protagonist sees the keys dangling from the guard's belt. In a comedy the bigger punchlines are often set up very early on in the movie and then repeated. I see DM's needing to do the same. Thus, any player paying attention (and sometimes even ones that are not) can and will see the difference - thus moving the game forward.
Personally speaking, I cannot stand it when a movie/book/game does not move the story forward. Side quest - sure. They are fun. They are better if they tie into the story or character arc. But just to have randomness to show the world is real is a waste of time. Any good storyteller can do that while also moving the story forward. So (sorry for the long-winded approach) if a DM is concerned about the batching, they can still batch, but need to highlight or emphasize the difference. It will not ruin the exploration pillar, it only makes it more noticeable. You secret door could sound like:
DM: The first three rooms you investigate are guard barracks. They smell like barracks too: sweat, old underwear and stale air. You uncover little more than some personal items, guard clothes and guard equipment.
DM: The fourth room you enter is the same exact setup. But for some reason the air here does not smell. It's as though fresh air has been brought in.
This might be called telegraphing in your definition. But, in my experience (which may differ from others), I find the players appreciate this more than spending fifteen minutes on each room, making up a bunch of stuff like one guard's erotic story stash or another's emotional love letters, and then simply waiting for the players to say: "We search for secret doors" in every room they enter. Then me asking for a roll, describing the walls, etc.
As for ten sessions for a dungeon, I am sorry, I just couldn't. Let me rephrase that please: I couldn't unless the dungeon was full of story and lore and interactive NPC's. If it's a crawl, why spend so much time away from the actual story? I get that it might involve the story arc (escape from the Underdark example.) But couldn't it be accomplished in one or two sessions as opposed to ten? That's just my playstyle though. I appreciate and have had fun doing a ten session dungeon set once, but I am not sure I'd do it again.