I have had good (meaning totally usable) results from E-6 film as many as 15 years old. Usually there is a slight color shift, which is fine because I usually get expired film in large emulsion-matching batches that have been similarly stored, so I can test some first. I usually have E-6 films go a little tiny bit magenta. Based on expiration dates, it seems like the shift usually happens after about 10 years on refrigerated film. All of my post-2000 film looks like new. It is the early and late 1990s stuff that starts shifting a little. The older stuff, or stuff that has been questionably stored, goes even more magenta and starts to lack punch in the low tones.
With b/w films, I have not had a ton of luck, as I rarely use low speed film in b/w.
With C-41, I have also had good luck, even with high speed films (Fuji Press 400 and 800) about 10 years old that were not refrigerated for at least a few years before I got them. I have good luck with my late 1990s (if I remember correctly) Ektar 25, and it is not supposed to keep well at all. Old C-41 films seem particularly resilient in my experience. I would say that this is in no small part due to the latitude and ease of color balancing of color negative materials. They may actually keep no better than E-6 films, but making adjustments and compensations is easier and more reliable.