What if he tried that, but every day just got worse than the last day?
And people don't get any younger.
My grandmother is 98. She hates her life since she could not go out anymore. But she is catholic and suicide would be a mortal sin. So she waits till gods take her. And suffers till then.
I would make a different choice for sure. If life is hell and no one depends on me, why should I continue the suffering? (At the cost of others, if I would need help?)
But my plan is of course to reach 120+ in good health. But if I decide I had enough, it will be my decision.