I guess best analogy would be a senior coder, who was promoted to a managerial position and not allowed to work on code. Upon retirement, he created a one-person app/saas company.
Can you at least specify the field in which your father innovated?
I'm interested in free culture and getting more free stuff out there, so I do some stuff on Wikipedia / Wikimedia Commons and Project Gutenberg.
Theoretically I could contribute to open source software, but there's no project in particular that motivates me at present.
It was a rather gradual transition from him working hard every day and an occasional weekend, to not doing much at all.
He did some traveling, then started fixing and renovating the dacha/summer house, reading books, pestering me to explain how this or that internet or tech thing worked, and so on.
On the personal side, he became much more relaxed and less snappy/irritable.
My kids tell me that I am no longer grumpy. I feel better about myself.