As a founder you would probably spend more time on calls and other administrative tasks that don’t require much brain energy. That’s how you end up doing long hours.
I think this is an important comment. I used to be a late night worker but family and other commitments has made that impossible. I wake at 5AM to get a few solid hours of brain work in before the family stirs. This has been the best approach to retaining the 'late night work hours' and balancing family.