Are you sure that the expiration date is not checked for any vendor? I recently paid online (Mastercard I think) and the transaction got declined because I entered the wrong expiration date. The date was in the future, I just entered a wrong month. So there must've been a check. But could be that they used 3D secure (or equivalent) and it got declined there, the check often happens too fast to notice.
I believe this comes down to the cardholder bank. My local credit union doesn't check expiration date of cards (I've tried as far out as 2029). CapitalOne does.
