It is true that quality is more important than quantity. But somehow in many cases people do use that as an excuse to slack off, and on the contrary, people delivering the best quality also those that do not skimp on quantity. If somebody knows how to do his thing in an excellent way, he'd probably also stay after 3pm on Friday to finish his thing. If his mind turns off at 3pm, then maybe he wasn't turned on too much even at 2pm. At least where it concerns professions which require personal engagement, if you just dig holes 9 to 5 (to 3 on Friday) then it's different of course.