“Every now and then we have to reprocess the fissionable material in the nuclear warheads to make sure we have stuff that works and not just duds.”
Actually we don’t. From time to time we modernize our nuclear warheads by building new warheads but the fissionable material does not degrade.
The laws of physics have not changed ~ the “fissionable” material does degrade ~ which is why we call it “fissionable” and why it has half-lives.