[I see my hands]

"I had a friend that built an underground room and stocked it with a months supply of special canned survival foods, costing quite a lot.
They all expired, before he died."

I'm not buying it. Someone serious enough to build an underground facility thinks in terms of years of provisions not months. And he knows to buy provisions that have shelf lives measured in scores of years.

[AlexW]

“I’m not buying it. Someone serious enough to build an underground facility thinks in terms of years of provisions not months. And he knows to buy provisions that have shelf lives measured in scores of years.”
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Nobody is asking you to buy anything.
This was maybe 25 years ago.
He proudly displayed the concrete walled room, about eight feet below ground, full of shelves with hundreds of large cans that he had ordered from a survival company.
No doubt that the technology has improved since then.

That being said, I can imagine buying foods that have a shelf life of years, but I really can not imagine someone being hunkered down in an emergency situation, in one location for more then some weeks.