If it uses a deuterium-tritium "zipper" for a neutron source, it's good for about three months. If it uses a polonium neutron source, it's only good for 14 days.
(Note: tritium costs about $50,000 a gram. Polonium is likewise extremely expensive.)
If it uses tritium boosting, the tritium has to be changed out every few months, or it will decay to helium, which will absorb a great deal of neutrons. (Some of our 1950s nuclear weapons tests "fizzled," i.e., did not generate a nuclear yield, because of helium contamination.)
Going on, firing set batteries and capacitors need to be changed out every six months or so; the explosives need to be inspected and replaced every six to nine months (they are wrapped around a lump of plutonium that generates constant heat; eventually, volatile compounds will evaporate out of the explosives, causing either the explosives to not detonate properly or to lose their shape around the pit; either condition means that the spherical implosion wave (necessary to bring the plutonium to supercriticality) will not be formed properly.
Wiring and detonators need to be checked annually for signs of wear or corrosion and replaced as necessary.
Finally, the plutonium itself needs to go back to a nuclear weapons fabrication facility every ten years due to americium buildup from decaying plutonium.
The USSR is unable to account for hundreds of "satchel" nukes. Are they impotent?
Unless they've been remanufactured from the core out, yes. See above.
"Unless they've been remanufactured from the core out, yes. See above.
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Well my BS-Physics is 38 years old and I have forgotten most of my nuclear physics 'stuff' I bow to your current knowledge.
Thanks