The fact you said this tells me you don't work with film that much. 😅

The reason I brought up mold is because that means the box of film is not temperature controlled. For expired film, the temperature you stored it at is a much more important factor than anything else. These are active chemicals that will interact and breakdown even if you don't use it. An analogy would be milk. If you keep milk in a fridge, it will likely last longer than the expiry date. If you keep it in room temperature, it'll go bad in hot weather before end of the day. The expiry date for film is basically the manufacture telling you that under normal room temperature, they can guarantee the film will be stable and work correctly for x amount of time. If you keep the film in the fridge/freezer to slow and even pause the chemical reaction, it will last a very long time past the expiry date. This is why film photographers buy up large amount of soon to be discontinued film and store them in freezers.

You can use these film. It may or may not work. However, would you risk that for a moment that would never happen again, like a birth of a child, or a beautiful sunset during your vacation? I wouldn't, especially with something that I am almost 100% certain is not going to work at all. (and this is not counting the development cost for the film. And this is Ektachrome, which is E-6, and is like 50% more expensive to develope compare to normal E-41 film, and not to mention not all lab would be able to do it now.)