Many manufacturers will sell and advertise emergency preparedness food packs to still taste "great" 25-30 years into the future (or at least maintain a consistent taste over this period).
For instance, they will cook eggs, lasagna or vegetables (anything really), then place it into a freeze-drier unit, which eliminates the water via sublimation. They then place the food product into a mylar or aluminum pouch (sometimes polyurethane), insert an oxygen dissector pouch in it, then instruct the customer to store it in a cool (less than 16 degrees Celsius or 60 Fahrenheit) and dry environment for long term storage.
What process happens after 25-30 years which limits its shelf life? It is the accumulation of oxygen diffusing within the bag over time? It is the oxygen pouch that reaches it absorption limit? Is moisture sneaking in? Is the organic structure of the food break down due to normal thermodynamic forces over time (increase in entropy)?
What if one wanted to increase the shelf-life to say 50 years, maybe even 100 years? What food break down processes will be encountered as the limiting factor, that would need to be countered?