system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5- Do nuclear weapons expire?
gpt
Not just do the cores themselves degrade over time, the actual machinery in a nuclear missile will degrade rather quickly over time.

The missiles also use particular types of fuel that is highly corrosive, so they can't be kept fueled all the time.  

Basically, the whole process around a single nuclear missile, its silo and all the support equipment is very sensitive to degradation over time.  It's extremely expensive to keep these missiles in a ready-to-launch situation.