I just thought it was funny that we tried to rest because we felt tapped out, triggered the boss fight anyway and had less trouble than the previous fight in that room. Just shows how things don't always work out like you might think.
In the Pathfinder adventure path I'm reading, there's a large dungeon with a big boss fight... a boss that has nothing to do with the storyline; he's just standing on a secret enterance even he doesn't know about. And if the players haven't been paying attention they might not even realize it, and let the real villain (a much less powerful creature) make off with the treasure they didn't know about.