Given his age, that sounds reasonable.

Are you saying that "age" is somehow a reason to retire? Most professionals I know who are able continue to work as they age, perhaps with a somewhat reduced work schedule. There's nothing I know of which keeps the mind sharp than the need to solve Real Problems. Figuring out which golf course to try, or which TV channel to choose -- those don't help too much to reduce cognitive decline.

Yes, age is normally the reason people retire