Tony Bennett, because at 82 years old, he still sings as mellow as he did in the 60's. He is a perfect example of a singer that takes care of themselves and their voice can sing as long as the do stay healthy. Andy Williams in another who fits this category.
So many singers have ruined their voice by sing incorrectly for a long time, or did not take care of their voices and it is embarrassing to listen to them try to sing now.