I'm young so I don't have much input but I have a friend that is in his late 70s and still dives regularly in New England. Not exactly easy resort/vacation diving. He says it's all in the mindset. His friends are all retired and sit on coach and do nothing. He has bad knees/hips but still finds time to dive locally and go on 3-4 dive trips a year.
I hope to be doing the same when I'm his age or possibly older.
I hope to be doing the same when I'm his age or possibly older.