If one decays. If they do find a reason for the body to basically stop renewing its cells (and make it so they keep renewing when they would normally stop), then one would live longer (you still might die for some other reason we don't know about yet), or at least you could stay active for longer, as I've been under the impression of late that people die when they get old, not just because their body is shutting down, but also because as it shuts down, they can't do the things they enjoy. They get bored with life. My 94 year old grandmother is getting to this point, and by late grandfather likely died because he gave up...couldn't see very well, couldn't hear very well, couldn't walk very well, and his hands didn't work very good. He couldn't read his books, he couldn't conduct the orchistra, he couldn't work in his shop (he was an engineer), and he couldn't hear the television. My grandmother is slightly better off, but she body is just starting to fail her.
If one could still do the things one enjoys doing, then one might have a reason to go on living. But to do that, the body has to at least fuction properly.
But..."people die when they are killed".
