If they had them, and that is a big if, to say they have the supplies to keep them up to spec is a stretch. They certainly possess some of our stingers left over from the russia/afghan conflict, yet they can't keep them up to spec, or they would have put down signifcant numbers of allied aircraft in the past few years. Nuclear weapons are infinitely more difficult to maintain, not just in terms of materials such as tritium(which is needed for the triggering mechanism, and has a relatively short half life), but more importantly in terms of the expertise needed to keep them operational.
It depends on the trigger, and the style. Tritium is typically used. Some may even use the polonium style, but that won't last much longer.
However.. The big thing is, maybe they can be refueled by the bad powers. I bet NK has quite a bit of Tritium now.
And for a real downer, a fizzle with no 'trigger' will detonate at minimum 10x Oklahoma City's bombing.
And you know what's worse? Uranium guns like Little Boy apparently do not need neutron triggers at all. That's 10-18kt of easy power, and look at the Graple tests. A small artillery shell can contain enough Uranium for a gun-detonation and delivery 15kt.