Once I quit my day job and started consulting, I became deeply aware that most of my usual 8 hour work day is spent doing anything but coding/doing billable work.<p>Now, after a couple years of self-employment, I feel accomplished if I manage to work (i.e. bill) 4/5 hours a day. Paired to an appropriate pay increase (I'm still billing by the hour -- I know), that's the perfect amount of work to avoid any kind of mental burnout.<p>More than 5 hours and I'm mentally dead until the next day.<p>Maybe there's something wrong with my work ethic, or I'm working on exceptionally hard projects (they are not, but I spend most of my time creating and deconstructing abstractions in my head than actual code writing, and that burns an incredible amount of energy), but that's also what scares me when I entertain the idea of getting back to a full-time job: I really don't think I can handle 8/9 hours working, I would feel like a fraud being that I'm mentally able to be productive only 50% of that time.<p>God forbid working 12+ hours in one of the usual big companies.