Shelf Life of Matches

I was going through a closet and found a book of those green matches that come in MRE's. The cover says "designed especially for damp climates", so they're obviously better than run-of-the-mill book matches, but I don't know how much better. 

Anyway, I think the last time Uncle Sam fed me an MRE was the summer of 1991, so they were more than 16 years old, possibly quite a bit more. They all lit on the first strike.