It may be a little off topic since I'm gonna talk about army
C-rations but I ate some in 1976 and after we ate them we looked at the dates on the cans and they were manufactured in 1953. I don't know whether they treated the c-rat cans any different than any other canned food but if it didn't kill me after 23 years I would have to say any can without rust would be OK after at least several years.