If the PCs want to sit around for 20 minutes, why would you want to stop them? How does it make the game more fun to limit the use of healing powers between combats? This rule smells like railroading and I don't like it.
If the PCs are in an obviously dangerous or urgent situation, they shouldn't be resting at all.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.