I know of a "plodder" who loves her job so much that she is still there at 73, well respected, doing a fantastic job. She is passionate about it, and her hubby has retired.
We have a guy where I work who is 90 and he still comes in a few hours a day. He has his own little business, and certainly doesn't need the money! His body may be old and frail but he has an amazing mind, if I'm half as brilliant as he is when I'm 90, I'll be happy.