So they set the card to expire when you plan to check out. But I've extended my stay (and done late check out) and I didn't have to get a new card. Why did my room lock let me back in without getting a new or rewritten card?
I don't know about other systems, but with Onity systems you have to get a new card to extend the expiration date. Of course, it's possible they gave you a card with the incorrect expiration in the first place; happens all the time.