If I didn't have to answer email or deal with any middle management, this could work. But the paradox is that the only scenario in which legitimate optimal efficiency can be attained is in a small-group, highly-communicative environment (like a startup); in that kind of environment, you're putting in 80-hour weeks so you can get profitable as quickly as possible, so there's no way anyone is saying "I've put in my 25 hours, see you guys next week!"