For many years one of the most interesting camera shops in Portland was Hollywood Camera. Located in the Hollywood Neighborhood of Northeast Portland, it opened in 1951 and had the same owner until he passed away in 2019.It closed and it's many treasures were scattered to the wind.
Earlier today, I was at a different shop and talking with the clerk who has been my go to guy for decades. He told me a story that about ten years ago, he was in Hollywood Camera. He had been a regular there for years and he asked the owner about some of the film on the shelf. The owner pulled a hundred foot roll of Tri-X off the shelf and handed to him. It had expired in 1966. He used the entire roll, exposed it at box speed and got great results.
Your results may vary.
Actually he got lucky w the 100ft roll as he would have been able to test a little bit of it to see how it needed to be exposed, before shooting the rest.
You really don't know until you shoot it. Here is a shot from a roll of ancient Kmart film that RoamingScott sent to me. I did not play around with the colors, this is how it came out! (rated it at either 25 or 50 IIRC)
And this is from a 25 year old roll of Kodak Supra 100 that I rated at ISO 25. To my eye it looks perfect and I never would have guessed it was that old:
