In adventure-based design, taking a rest (in mechanical terms) is something that needs to be earned, and can't just be taken whenever the party decides to. They could sleep whenever they want, but they only regain resources when it is "safe," and "safe" only happens when the DM allows it (or when the party completely retreats, ending the adventure).
Rather than have the rests "earned," you might have the adventure be reactive, meaning that rests lie in the hands of the players, but taking extra rests might be a problem.
In this model, using 4e as a base, the adventure has a number of "free rests" that the party can take, whenever they decide to take them. By default, this would be 4. Smart play and using sidequests might raise that number. If the party exceeds that number, the adventure reacts:
- Extra Tasks: The adventure produces two extra Major Tasks for every extended rest over the limit. A necromancer, for instance, may animate more corpses, while a warren of goblins may get reinforcements.
- Harder Tasks: The level of the Tasks left increases by one for every extended rest over the limit. This can increase the level of each monster in an encounter, or the DC for each skill check in a skill challenge or a series of skill checks.