I have two modest prep stores: Canned goods and related stuffs that I rotate through as part of my normal diet and dehydrated stuff that is frankly too expensive now to rotate but are guaranteed to have 20 years of shelf life at full quality.
I ate a 10 year old MRE once, other than the cheese spread separating out it was fine.
I have staples prepped for long term use, I do not touch them. I am sure they will be fine, they are stored under ideal conditions and its pretty well known how they store.
The bulk of my preps are day to day items that get rotated. The plan is to suppliment that with my long term as well as whatever I can kill, forage or grow. Its far from sustainable but I would outlast 95% of the population before it was exhausted.