4e is a game of resource attrition. I can't find the quote in DMG right now, but from memory and experience, it works best with about 3-5 combat encounters in an adventuring day. That way, some of the characters will risk running out of healing surges, dailies will have been used up, etc. Methods for creating a sense of urgency to make players push forward and go through these encounters instead of taking an extended rest after each one have been discussed here and elsewhere.
My question is about tackling this issue from another angle. Consider a situation in which it only makes sense, story-wise, to have one combat in a day. Something the PCs encounter in a week of traveling, for instance. Presume you don't want to dedicate a whole gaming session to dealing with it by creating 3 encounters around it just for the sake of having 3 encounters.
How do you make this single encounter mechanically meaningful? Raking up its difficulty is not necessarily good story-wise, and unnecessarily drags out the fight. But a regular encounter will get nuked off the face of the map with dailies without ever threatening PCs.