[spaceman_2020]

Personally, I feel that it's too little.

No one is perfectly productive. If you devote 40 hours to something, you're going to spend at least 10-15 hours out of that on non-productive busywork.

There are also some tasks that just require extended periods of focus before something "clicks". No way I could write or code if I was told to pack up and leave after a fixed amount of time.

Also, I've always found that when I'm working hard, I'm more creative in my hobbies as well. I make music as a hobby and whenever I've taken a break from work, the music just doesn't flow.

Caveat: I work for myself so the work is both important and enjoyable to me, and I don't have to deal with office bureaucracies. If I was working for someone else, I might have different views.