I think how many hours per week you can work is an individual thing. I need atleast 7 hours of sleep to think straight and produce meaningful stuff (code, designs, conversations, etc).
I don't need seven hours of sleep to think straight and produce meaningful stuff. I need seven hours of sleep to be able to convey the meaningful stuff to other people. I tend to talk a lot faster than people when I haven't gotten much sleep, and change subjects pretty quickly.
