Earlier quoted context omitted.
>Sorry, I must disagree. Two people working 20 hours a week are refreshed, not burned out, have time for educationally side projects, etc. Take a look at Brooks' The Mythical Man Month for data that demonstrates the opposite, at least in programming; I haven't followed the field closely, but education and industrial organization researchers have done similar work in other professions.
Brooks' was at IBM, they adhere to a 37.5 hours per week work schedule. Programmers who can produce 3-4 hours of real work per day are considered productive. Any more and you will start to burn them out.
I mean officially I was there 37, it was a good week if I was doing real, actual work for 20. Yes, I made up for it by working my tail off when it was needed.
We coders can be absurdly productive for short bursts, or be slow and steady. You can't have massively productive and steady for very long. In your early 20s you have a few years of this, but the more you push it then the more jaded you'll be later.