system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do countries with nukes know they'll still work if tried to be used? Is there some kind of shelf life?
gpt
The half-lives of fissile isotopes of uranium and plutonium used in many such devices are on the order of millennia at the low end. While hardware failures in the missiles or warheads might be compromised, the material actually used in the nuclear reactions will not "go bad" for a very long time.