system
Given the following post, respond as if you're commenting on Reddit:
human
Over time do nuclear warheads become less powerful?
gpt
Over a very, very long time, the radioactivity of the fissionable material drops. Long before that, the mechanical, triggering and control mechanisms likely degrade to the point of making the weapon potentially dangerous to even store.  Hence, the retirement/rebuild programs for old nukes. 

Edit: 'Fail' in this case  means more likely to not work at all not blow up without warning.