Lifetimes of nuclear weapons and their deterioration with age is thoroughly studied and was one of the drivers of development of supercomputers starting with th

Lifetimes of nuclear weapons and their deterioration with age is thoroughly studied and was one of the drivers of development of supercomputers starting with the early 1990s when nuclear testing was stopped. Ongoing work on rebuilding plutonium cores in the US is driven by their predicted deterioration with age (as helium caverns accumulate in them), making their behaviour less predictable (even if not knowingly worse). And new nukes are built every year, just in low (~10 a year) quantities - fully from scratch. In addition to refurbishment work for much larger numbers of them.