Although, Denny and I believe Kai have shown that the temp of your sparge water/doing a mashout has very little effect on efficiency. Some sparge with warm or even cold water.
The true purpose of a mash-out is to stop conversion by denaturing all enzymes and thus lock in the sugar profile (dryness vs. mouthfeel). Of course, if you batch sparge the grain isn't sitting in the tun long enough to really convert much more while you sparge. Commercial breweries that fly sparge over several hours tend to mash-out, though.