That's not what I would conclude from the original post.

In fact the OP pretty much demonstrated that his 79+ year old powder, while looking and smelling okay had already deteriorated to the point where it was igniting/burning inconsistently.

I have 40 year old powder that has deteriorated in a similar manner.

Smokeless propellants are very stable compounds with a long shelf life, but regardless of how well it is stored, it does not last forever.