I've been thinking about it and I think my Player knowledge at the start of the campaign made me cautious, because I knew I had maybe 7 days before I'd become a mindflayer. That seems to be an incorrect plot assumption, but what if we were presented with timers for the major events along the way? At first a timer to say you'll become a mind flayer, then a timer for the druid grove internal tensions to erupt, then a timer for the golbins to attack.. all counting down in days, with the consequence being that the plot moves on without you. Maybe the druids expell all the tieflings, and they get slaughtered.
Another simple idea is that if the game decides you're resting too much that you get attacked at camp, like a DM might do if his PCs tried the same thing. You can then warn the players that they're resting too much and they need to make progress in the game before they rest again, or the attack might repeat. It'd leave some flexibility to rest if you've over-extended yourself for a few encounters that day, but if you make a habbit of it the game starts to deny you these rests.
