I've often thought we're doing something fundamentally wrong by treating programming like any other office job, or even like a "production" type job like manufacturing. It's of course nothing like that - as you say, the mind doesn't have the same recharging characteristics as the body. I get the feeling people maybe compensate for it by having a lot of downtime in the day where they're kind of pretending to work, but I would find that maddening. I'm either working or I'm not, in which case I want to be free to do what I want without someone looking over my shoulder.