This bit about the cool people dying young is nonsense. Certainly there are myriads of uncool people who die young.
As for people who are(were) just as cool (or even cooler) at an old age: Paul McCartney, Stephane Grappelli, Maggie Smith, Vladimir Horowitz, Clint Eastwood, Samuel Jackson, Leonard Cohen, Michelangelo, Orson Welles, John Wayne, Sean Connery, Ella Fitzgerald, etc etc.
You forgot Roger Moore. Keep in mind, I said before that most people are not cool at all. So even the young cool people are total exceptions.