“Wow, they’re still going!” We’ve probably all thought it or said it. A story appears in the media reminding us that there’s a small group of people who never seem to retire: Musicians. To name the most obvious, Bruce Springsteen in his mid-70’s, Paul McCartney into his 80’s, and two of the remaining Rolling Stones, Mick Jagger and Keith Richards into their early 80’s. We all might marvel at how they’re still going, but the question would be why are they still going? Money? Unlikely, as estimates suggest they’d all be billionaires, or close to it. There’s little they couldn’t…