The temperate in the burn chamber get up to 3,000F.
So anything that has a melting point lower than that will burnout sooner or later.
Then there is also oxidation/rust, from the water/air/organic moleclues/high temperature involved.
So sooner or later it will need to be refurbished.
However if we know that it will last 10yrs+ then we can just replace it in the summer (or when we have extra money) before it fails and we really need it in the winter.