Anticipating the next post and pre-emptively answering....
"If I can get 80% on no sparge, why would I ever want to sparge?"
Efficiency is going to start falling off faster on big beers due to how much grain you end up using and therefore how much high gravity wort is going to remain in the grain.
Further, it requires a mashing vessel that can hold the full preboil volume, plus the volume of absorption, plus the actual grain.
If you tun is big enough and your OG is moderate, no sparge away.