If anything, Post-ops rather live longer, if approaching the topic strictly from a biological point of view and ruling out any Psychological state, as the Metabolism in a Post-op is lowered, which is also the reason that females statistically speaking lives for a few years longer than males.
It is also a fact, that castrated bio-males lives longer than both females and males, probably because they have lower Metabolism than both of them, and also avoids some age-deseases as a result of the Castraton.
However, Castrated males also run a greater risk to develop some other conditions, such as Osteoporosis, for example.