Trust me, rehab isn't a vacation or a picnic. The whole point of it, really, is to remove the distractions that derail so many people in the beginning. He is probably doing chores, has assignments to work on in between group sessions, etc. I've never been to rehab, myself (at least not as a client) but I know many people who have, and I've led meetings in them.
YOU are getting a big break, yourself, from the insanity. However much you might like to have the concentrated dose of recovery he's getting right now, you are still getting a lot more peace, I'm betting, than you had when he was there.
He'll be dealing with "life" soon enough. Hopefully, what he is learning at rehab will enable him to cope with it better than he was doing when he was just staying dry for periods of time before this.
Hugs,