I probably work 35-45 hours in the office. But as an owner with extra responsibilities and devotion I can easily add an extra 20 hours every week.

Usually around 50-60 hours a week. You get a lot of freedom as a startup founder. So you can be flexible, but there's no way around the fact that it's hard work and not for everybody.

40 hours per week. But I have other important interests so Im really pushing for 35 hours, ideally 32.

At my last job, that I had for a while, we were required to bill exactly 40 hours (or the equivalent, given that we had bi-monthly pay periods). Any less and we'd get contacted by corporate (only happened to me once, because my line manager had me work more the previous pay period). Any more required customer approval, at least in the later years after someone (me) worked too much.

The one before that was roughly 37.5 hours, but didn't require detailed timesheets.