[overgard]

35 or 50 hours or whatever is a pretty arbitrary number, I would agree most people have different limits on how long they can work, but I think the larger point is that for intellectual work, more hours don't imply more output. Or at least, not sustainably.

Not at my current employment, but I know there have been jobs where, say, 3:30 would roll around and my brain would pretty much fried for the day, but I felt obligated to stick around for an extra hour and a half because I'd get disapproving stares if I peaced out early. That extra hour and a half the company got of my time as not a useful hour and a half though. Or conversely sometimes I'd stay late because I was engaged with some sort of problem. Either way, the number of hours really had very little to do with my productivity, and trying to "force" it was never particularly useful.

If I were a manager, and I saw a person was treading water, I'd rather them go home and have them come back the next day refreshed, rather then have them stick around being miserable to meet some arbitrary number of hours.