[Southack]

The atomic isotope used for nuclear triggers has a typical half-life of 90 days or less. The useful life for the booster isotope (normally tritium) is typically 8 years or so. The core lasts longer, of course, but you've got to have it all for it to do something more than simply fizzle into lethal short-range bursts of radiation and heat.

And even replacing the electronics and conventional explosives is more than meets the eye. You've got to avoid letting much air touch any of your heavy metals (forms rust rapidly), you can't let any vibrations shattle your fragile heavy metals (they are among the most brittle of all metals), and you can't move your core too close to your "bullet". Nor do you want to induce any electrical currents into your circuitry while you are doing your maintenance.

[AgThorn]

fascinating. Obviously, you have a lot more knowledge in this than I.

I was always under the impression that the 'triggering' material that might deteriorate would / could be something simple, or should I say more readably attainable, like c4 or the like.

Perhaps this is not possible. Which is a relief, I must say.