If the players are sensing that level of futility, then you need to have them deal with breakouts. Let them recapture a couple of those guys when the escape attempt happens, unless something happens where everyone gets out. And YES, this happened, for a variety of reasons, mostly not paying attention to who was imprisoned, how they were imprisoned, what they did with their free time, and an unlucky accident. This triggered an incident where the entire prison burrowed away. Well, most of the villains escaped. Literally, this had never happened before, although they were really mad, they couldn't dispute the logic of what happened. Always point out in these situations that things might have worked out differently if someone in the group had said something. If not, they have no one to blame but themselves.