A rule of thumb that seems to apply here is that the last veteran tends to die around the time that the 100th anniversary of the war is approaching. There are some slight variations, and human lifespans have been generally getting longer, but that's been the general trend for the last hundred years or so.
No, it seems that the last veteran tends to die around the 90th anniversary of the end of the war. It seems that the probability of living beyond 110 is negligible, so it seems that's the maximum age people around 20 when the war ended can reach.
