Actually, I never had a group with that 15-minute-adventuring-day problem. We were roleplaying, and the wizard and cleric (me) would never think to suggest stopping at 11am so that they could refresh spells.
This isn't to say that the phenomenon wasn't a design flaw. But in most D&D games I've played, you'd never see anything equivalent to Alterac Valley where the PCs blatantly ignore the (designer/DM)'s intent so that they can rack up loot in the most efficient manner possible. (If nothing else, the DM wouldn't stand for it!)
All this really means in game-design terms is that flaws and loopholes in D&D mechanics are less likely to become huge issues like they do in MMOs, because D&D is human-adjudicated, and a good DM won't let you get away with egregious asshattery.