Remember, under all of this is the rule: you can only take one "extended rest" per 24 hour in-game period. Keep track of the time passage during the adventure, and stress this to the party. If they set out at eight in the morning, get to the combat by, say, 2 p.m. and after a furious five minutes of fighting they decide that they need another extended rest... well, let them know that they will need to wait until midnight to begin it. Sure, give them the option to back off, find a secure spot to rest, etc., maybe even figure out a way to watch the entrance to the bad guys' lair, but also let them know that the noise of their fight was enough to tip off their presence, and that while the party twiddles their thumbs, other things are still happening. I know if I had a group of mortally agressive intruders in my dungeon home, I'd not be simply content to rest in my den after killing my family dog so that they could be fully refreshed to come and kill the rest of my family.
Perhaps, given warning and time to prepare, the villains raise up their defenses to such a degree that the delayed adventuring faces an entrenched wall. Taunt them with it like the French knights in Monty Python's Holy Grail.
Maybe there was a back door, and while the party rested on their laurels, the villains closed up shop and ran away taking all the treasure and XP with them.
And of course, the villains could also mount an attack on the intruding party while they're resting. Don't be afraid of doing this, but also be willing to have the villains push for the party to surrender instead of fighting until PC death.
Let them know that while yes, their characters are the heroes/protagonists of the story, that the world doesn't revolve solely around them, and that choices have consequences.
Give them a recurring bad guy whose M.O. is to put his underlings between him and the party, and run away before the party can put the kibosh on him. It doesn't even need to be the main boss -- even better could be a second-in-command, major domo string puller who knows how to get while the getting's good, because he knows that in a direct confrontation with the party he'd hold up like a sub-prime loan. Let just this one underling escape the adventure, but then show up again in another adventure later, working for a new big boss. Wash, rinse, repeat. I guarantee you that your party will want to get this guy. Give clues that by resting, they give him the time he needed to get away, and they should figure out that they want to press on.
*****
Beyond that, for constructing encounters, help them realize that there are more ways to get the upper hand than simple HP count. Bring in lots of controlling aspects, and introduce non-damaging hindering conditions like "blinded" or "total concealment" which preclude your party members from seeing each other (it's hard to heal someone you can't see.) Use traps and terrain to put them in compromising positions that they can't just heal their way out from. Have enemies focus fire on one PC, so that it gets to a point where only one character really needs the extended rest.
-Dan'L
Perhaps, given warning and time to prepare, the villains raise up their defenses to such a degree that the delayed adventuring faces an entrenched wall. Taunt them with it like the French knights in Monty Python's Holy Grail.
Maybe there was a back door, and while the party rested on their laurels, the villains closed up shop and ran away taking all the treasure and XP with them.
And of course, the villains could also mount an attack on the intruding party while they're resting. Don't be afraid of doing this, but also be willing to have the villains push for the party to surrender instead of fighting until PC death.
Let them know that while yes, their characters are the heroes/protagonists of the story, that the world doesn't revolve solely around them, and that choices have consequences.
Give them a recurring bad guy whose M.O. is to put his underlings between him and the party, and run away before the party can put the kibosh on him. It doesn't even need to be the main boss -- even better could be a second-in-command, major domo string puller who knows how to get while the getting's good, because he knows that in a direct confrontation with the party he'd hold up like a sub-prime loan. Let just this one underling escape the adventure, but then show up again in another adventure later, working for a new big boss. Wash, rinse, repeat. I guarantee you that your party will want to get this guy. Give clues that by resting, they give him the time he needed to get away, and they should figure out that they want to press on.
*****
Beyond that, for constructing encounters, help them realize that there are more ways to get the upper hand than simple HP count. Bring in lots of controlling aspects, and introduce non-damaging hindering conditions like "blinded" or "total concealment" which preclude your party members from seeing each other (it's hard to heal someone you can't see.) Use traps and terrain to put them in compromising positions that they can't just heal their way out from. Have enemies focus fire on one PC, so that it gets to a point where only one character really needs the extended rest.
-Dan'L