We're running an official AP that's at times brutally hard. At these times, more than half of the party has ended encounters at less than half hit points. Since the next encounter might be just as hard, the only way they would go deeper into the dungeon was if allowed to heal up fully, which (after much clutter, choice anxiety and calculations) translates to "half an hour to two hours later".
The sandbox option to throw in a couple of low-level wandering critters to make the party get a move on never felt appropriate - I couldn't in my heart punish them for getting smashed up by brutally hard encounters, could I?