I've been looking into jobs that work few hours but are highly qualified and they're usually outside consultants that get called in a couple of days a week. Apart from them there was one person who worked in a refinery that only had to be at work 20ish hours a week. She spent most of the rest at home on call or simply working from home. I recall that she enjoyed it.
I've never been able to get up after a day of work and do something. I'm just done after working for 8 hours. I'd just sit and do nothing wait to recover "energy" and as soon as I recover back to normal work starts again.
6 hours without reddit, hacker news, meetings, and other distractions, beats 9 hours with those things (as long as you're working on the right thing and not throwing away ALL your time :-)