[musicale]

> It's my experience that at most 2-3 hours is productively spent, the rest is wasted.

That sounds about right for most workplaces I've been in, and it's probably a fairly sustainable pace for work that requires careful thought and concentration.

I remember reading about a consultant who advised struggling graduate students to spend no more than 18 hours a week working on their dissertations; on this schedule most of them finished in 6 months or less.