Butane canisters do not expire or go bad.
As long as the butane canister has never been used or opened and has remained sealed and hasn't leaked out the butane will remain good to use for many years.
I've had butane canisters that were 10 years old and they were still good to use.
Once the butane canisters are open the butane can start degrading and not be able to burn as good as it's supposed to.
But the butane will remain good enough to use and does not expire.