Attached is some 6x4.5 Kodak Plus-X (125 ASA) expired in 1962, shot at box speed and processed in my custom developer EXG1 (gives rodinal-like grain levels). There is a small amount of base fog, but honestly surprised how well it held up and that box speed processing actually gives good results. I suspect it was kept cold in a fridge, but not frozen since purchased. I got it from an estate sale with a ton of other film in similar condition. I have like 17 more rolls of this to shoot through.
Also good to know that Kodak HIE actually has a chance. I have one roll of that in 35mm with expiration 1967 from the same batch. I was going to assume it was long gone, but maybe I'll actually try shooting it a stop slower than box speed and hope for the best. I also have some really old E-4 process aerochrome but that I assume to actually be long gone, unlike the HIE