20-30 year shelf life is reasonable if the food is left in a cool place and undisturbed. Things like grains can last quite a while. I have stocked some rice, wheat, barley and legumes and am still eating my way through the first 5 lbs of each, except rice which I tend to eat more of. I love grinding my own flour for bread.

Eating out of buckets I'm more skeptical of - a family of 4 may eat 9 months of freeze dried food but they won't like it; although if the choice is between starving and eating freeze dried foods, they'll eat it. That's where I think the synergy comes between Costco and this type of long term, last ditch nutrition: the place is full to the rafters with prepared foods of all sorts. Folks who graze the aisles at Costco probably won't have too much trouble digesting these freeze dried foods over the long term.

FWIW my strategy is to stock foods my family regularly eats, and rotate them into our regular meals as much as possible; and as they approach expiration, donate the overage to the local food bank. It takes a little more space and management than a pallet of buckets, but is more edible.