MREs are irradiated for preservation.
There is nothing alive in the package, so they keep for years.
When I was in high school, I used to spend lots of time at the lab that developed the process. They had a peanut butter sandwich in a curio cabinet in the front office that had been treated a few years previously that looked fresh. 25 years later, the lab was shut down, and the property was sold to the city for a corporation yard. I stopped by as they were moving the furnishings out, and the sandwich was still there in that cabinet hanging on the wall, still looked fresh.
You can buy milk on shelves at room temp in Europe which has been irradiated and stays fresh on the shelf for months! I would imagine that if one irradiated foods and vacuumed out the oxy and replaced it with nitrogen, the flavors would remain stable for a long time. Wonder how salads would do with that treatment? ... I like salads.
I would like to see studies on long term food storage using irradiation, based on pH, proteins, carbohydrates, fats, and I’m sure other variables, like enzymes and catalytic agents.