I have no doubt that I could easily work more hours than I do now. But then I would have no time to do other things in my life.
I have zero interest in handing the rest of my free time over to my employer, especially for free.
I have zero interest in handing the rest of my free time over to my employer, especially for free.
If you're working on something you love and are good at, you're going to be productive longer. I think just measuring hours is missing the point.