As long as the star loves it, can still do it, and the fans still want it, there is nothing wrong with him/her performing well beyond retirment age. These rock stars obviously don't have to keep it up - they've made their mark and are millionairs/billionairs in their own right. They do it cuz they live it, love it, and the fans can't get enough. So I say, rock on!!!! And rock till you drop!!!