[Velveeta]

Wouldn't these nukes have a "shelf-life" and if they do, does anyone know what that shelf-life may be?

Perhaps just wishful thinking here.

[Calpernia]

Poohbah seems to have knowledge of that.

http://www.freerepublic.com/focus/news/1072462/posts?page=1298#1298

[NothingMan]

During the Cold War, these things were reportedly prepositioned (Mitrokhin). The question is how long can they sit dormant. They were placed in secluded areas. Probably not only to escape detection but to facilitate periodic maintenance.

But the raw material was/is the "core" problem.