I love MREs, and like I said, somewhere in the 1980s I too thought that they were about 3,000 calories.
Something that I do know about them is that they last much longer than the recommended chart for “guaranteed freshness”.
After worst case storage conditions in desert heat in the trunk, and way (way) past three years etc, the candy may be mushy and the gum maybe be chalky, but the important foods and the coffee and such are still plenty edible.
I have never seen a “puffy” MRE, but my understanding is that if you find one, then destroy it like you would a puffy canned food.
That’s good to know. Thanks!