I got 8 cases for a song last year, and keep them stashed in the storage, and some in the van.
If you've never had one, buy a few and try them all. They are heavily fortified, meaning you can live quite fine on 1 a day, if you have to. It's manufactured food, so it won't taste "great", but the quality has come way up since the '80s. Shelf life should exceed 10 years, in some cases 20 and still edible.
I wouldn't want to do what coinguy did, living off of them for an extended period, but with over 90 meals for my family of 5, we'd be okay for a couple weeks on the move, if it came to that.
The upside to them, is no required preparation. Open, and eat. There are water-activated heater kits if you want a hot meal, or if water is abundant you can just boil the bags in a pot before opening... then use the hot water for coffee, soup, or cocoa... or a bath, even.
I consider them the "immediate-ready" part of my long-term storage plan.