I don't have DU (yet; still waiting for a sale or bundle), but my plan is to just handle it like in TS2: because YA is optional in that game, a college sim would age slower than non-college sims (although in practice I send all teens to college anyway.) To make up for this, when I send sims to college, I make them finish first before continuing my rotation. So from the perspective of the home sims, it's as if the teens just aged from teen to adult (but with a degree and more life experience.)
So in DU, I'll just turn aging off while playing with a college household until they finish the term. So it'll be like TS3 UL too. If I ever have sims go to college while staying with non-college sims, I'll keep aging turned on and just consider them part-time students who have other affairs to attend to at home.
