In all seriousness: I would tink it would depend more on the mentsl state of the hobbuyist. Anyone who can ot manage without a legal guardian, conservator etc. should be considered to be as unable to give consent as any minor.
On the cusp is the relationship with Nicole Smith and the really old guy she married.
There are some men in their 80s on here (myself not included) who are very highly regarded by a lot of ladies, and can probably see almost anyone they want to.
I saw a lady this summer who told me a couple of her regulars were in their 80's. She did outcalls to their nursing homes.
When I first got in the hobby I thought 50 would be the time to stop, that over that age it was too weird to be banging women in their 20s. I don't think that anymore.