Does anyone know if non-refillable cartriges of butane or propane have an expiration date? If so, what part from them goes bad?
They do not. Ideally the cartridges are filled with pure butane/propane. The only thing that could go bad is the container around it. As long as the container doesn't show any forms of corrosion it should be fine, there are some butane/propane containers that may leak after a certain period because of a rubber seal inside. The seal can eventually dry out and crack, causing small leaks that will drain the container, even though the gas in the container can't spoil, you wont be able to use it because of the absence of gas