I purchased a Canon FTb QL at an estate sale yesterday, and come to find out it had film inside. Kodacolor 400. This camera hasn't been used in years. How many I don't know. I know the husband died 10 years ago, and his wife became a recluse and didn't touch anything of his. Some people say he died 30 years ago. So I need to know how long does it take for this film to degrade and expire?
It is difficult to estimate how much the film degraded. It depends on temperature, level of radiation, exposure to chemicals, age, light leaks and probably other things.
As the film gets old, the exposed image fades away and at the same time the entire film gets a fog, that, if you are lucky, will be reasonably uniform.
If the film is already exposed, it would be probably reasonable to have it developed longer than usual. Labs can do it if you ask for "push processing". You can usually do 1 or two stops push. If your lab can handle that, you can cut the film in half, process one piece and decide if the other piece needs some adjustments. Even if the film comes out totally dark, you may be able to recover much of the information by scanning it and using Levels to the extreme.