A lot of people do the same thing their whole life and do it well. Even at high levels of performance and art. Maybe they are the exceptions that prove the rule.
But, I agree with you. When you can't do it anymore it is time to stop or change.
Robert Plant pretty much admitted in interviews that he no longer has the range he used to. He just can't belt out those sustained high range tones anymore. So he doesn't. If he can modify a song to accommodate for that he does. If he can't, he doesn't sing the song anymore. And he has altered his musical style to fit his voice as well. I don't like his new stuff but plenty of fans and critics do.
But, I agree with you. When you can't do it anymore it is time to stop or change.
Robert Plant pretty much admitted in interviews that he no longer has the range he used to. He just can't belt out those sustained high range tones anymore. So he doesn't. If he can modify a song to accommodate for that he does. If he can't, he doesn't sing the song anymore. And he has altered his musical style to fit his voice as well. I don't like his new stuff but plenty of fans and critics do.