The boss at one of my clients quotes that frequently. He is one of those determined to live forever or die in the attempt, so he (mid-50s) treats every physical activity like a sort of virility test. He has just bought this incredibly exotic S-Works carbon fibre bike and is engaged in riding vast numbers of K on it. Good for him, I say. I (74) personally am determined to grow old gracefully, or more likely ungracefully, or even better, disgracefully.
A work colleague was WC on 10000 meters indoors when he was over 50 (they have age classes) and among the 50 best at the NY marathon (irrespective of age). He now have a heart problem because of his heavy training. I doubt he will live for ever.