I keep seeing articles about the uselessness of working more than 40 hours a week, this one for example but I remember I read the same on Forbes and others. Does this estimate include the time spent on open-source or external projects? Reading these articles it seems to me that the reason is that "you burn your brain" and what you produce in the overtime has no worth.
However this is not my personal "perceived" experience. I still feel fresh to work on a different project where I'm not moved by deadlines or client requirements, but the simple quest for "perfection" or to learn new stuff. I find difficult to think that everybody working in opensource do it inside their 40 hours, or that they're jeopardizing their payed-job productivity.
Further more, not all the jobs are the same, and none of these articles go in details about the different duties, whether you're a broker or a teacher, the limit is the same.