Commenter Nylund notices that economists are a particularly long-lived species:
Is it just me or do famous economists seem to live a really long time?
John Kenneth Galbraith (98)
Except poor Keynes. I think the main reason Keynesian economics took a backburner was because so many his opponents simply outlived him.
But, besides Keynes (or any of the really old school guys like Ricardo and Say), its rare to fine a major economist that didn't make it well into their 80's.
Paul Samuelson, as I found out today, is in his 90s. Ken Arrow is 87. It's impressive. These guys have managed to maximize their utility by prolonging their capacity to experience it.