FormerlyHemlock
Hero
I've noticed that, when the individual combats are deadlier, players are more likely to push for a long rest before coming close to their daily budget. Players spend a disproportionate amount of spells and resources in deadly fights, and it is harder for PCs to spread the damage out in one encounter, so one character is more likely to get mostly wiped out early. There's also the reasoning that, "another one of those will definitely kill us", as opposed to, "we can probably squeeze another little combat in before we try to call it a night."
Frankly, that sounds like entirely rational behavior on the part of the PCs.

I've noticed in my own games that what makes players reluctant to push on is not so much resource depletion as uncertainty about threats, and about their own capabilities. Once they've "solved" an encounter (a 3d6 CR 1/2 giant worker ants plus 2d6 CR 2 soldier ants--disable with Hypnotic Pattern and Web, kill ants who saved successfully first, kite and defeat in detail) it doesn't matter so much how Deadly it was, they're eager to tackle it again even if it seriously depleted their resources. But not having a strategy in place, or not understanding the threat, stops them in their tracks.
This is also rational behavior but I have yet to get the players to the next step, which is to notice why they are stumped and to undertake reconaissance to correct their ignorance. (Hmm, Chrome doesn't know how to spell "reconaissance.") Currently they just shy off and abandon the objective. I'm letting them have lots of easy practice combats (using a magic item which is effectively a training simulator) which I hope will have the side effect of making them more confident about undertaking recon. Already they've learned the virtues of Hasting the monk.
