Maybe I’m crazy, but I feel like I would get really bored if I were to retire and stop working altogether. I’m in the very fortunate position that I really enjoy the work that I do so that obviously helps. I also love the interactions that occur while working on projects and in business that I’m not sure you really get once you’re retired.
I also know a number of older folks (70+) who kept working and it seems like they are still quite a bit more “with it” because they have work to keep them motivated. That’s not to say there aren’t retired people like that, but my sense is that it’s more common among people who keep working beyond retirement age.