[zenhack]

The trouble is that this assumes pre-determined quantity of work. The reality I've seen most in places is that there's no end of stuff to do. The work is never "done."

What there is instead is an expectation of how much work you're supposed to get done per unit time (albeit calendar time in shops that have things more together). But this is in turn informed by how much time you are expected to devote to work vs other parts of your life.