[markus_zhang]

I think you have to figure it out with him because people on HN know nothing about your dad. I'd say ask him what he is going to do with that extra 40 hours first, find a field he is at least interested, and start from there.

For example I already know what I'm going to do after 20 years when I reach semi-retirement in late 50s. I'll probably start a retro video game streaming business and stream all those games from 55 years ago (that is from late 1980s and beyond if we count from 2040). I'll probably also start playing DND games seriously and stream that too if it's possible. I can also start publishing my own indie games and don't give a fuck about how much money I need to make becuase it is just fun to introduce some retro style games to young people then, many of whom have not been born yet.

But does this make sense to your father? I doubt.