What is the Shelf-Life of a Girl Scout Thin Mint?

There is an unopened box of thin mints in our kitchen cupboard. It's been there for quite a while... may be since last year. Or the year before. How have they survived this long?!! How have they not been eaten?

I bought a package of Peppermint Patties today (thin mint's older sister) and while Emmy's been napping on my shoulder, I have been daydreaming about uniting the thin mints and peppermint patties in a balls-to-the-wall chocolate mint explosion brownie. Sounds delish, no?

But how OLD are those thin mints?
The box doesn't have a "best if used by" date. The girl scouts probably figure they don't need to put expiration dates on their thin mint cookies, because they are (generally speaking) consumed mere minutes after they have been shoved into plastic sleeves and shipped off in their little bright green homes.

Should I just try one? What if I get sick from a "bad" thin mint? Will I never be able to eat a thin mint again without having horrible flashbacks?

I know this is probably an issue that no other person on earth has ever had, but if you have any wisdom to share in the girl scout cookie shelf-life arena, I'm all ears.