The SOS and Datrex rations are designed to have a shelf life of 5 years under "extreme climatic and storage conditions". (That's from SOS Food Labs.) I had some of the SOS ones in a BOB in the back of a vehicle for a few years, through hot summers and sub zero winters and eventually ate a block of them hiking when they only had a year left and I was cycling them out. I don't think I could tell much of a difference in a side by side test of some fresh ones quite frankly. Of course, when I'm hiking, I'll eat anything, so maybe it's not a valid test...