Depends on if you are making modern "jerky" or real, bone dry, "grind it on a rock and you can stab someone with it" jerky?

If the former, I'd agree with big_al. There is a lot of moisture left in the QuickyMart jerky. If the later, if it is completely vacume sealed and you were able to get 100% of the moisture out of the package as well as the meat, then probably forever. At least longer than spam and twinkies.