system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Is there anything you can do to stop a natural death? Does constantly replacing organs/parts of body work?
gpt
There already is, but the body just keeps finding new ways to die. 

Short version is most older people (60 range) develop heart conditions we treat with medicine. Now most 70 year old people may get treatable cancer. So now in their 80s, these people develop another condition we treat. In their 90s, they get Alzheimer's or Parkinson's. 

Hypothetically at age 100 they may develop liver and kidney failure. We fix that, 110 they may develop some new unknown disease and so on. 

TL-DR; You cure something that saves someone who's 80, when their 90 they get something previously unknown.