After being backcharged by HI Torino on a non-expired Chase free night cert 5 months after the stay, I would be very wary about using the cert post expiration date.

For you not be charged on the free night cert, not only when you check out the bill is 0, the hotel also needs to know how to bill the Club on this stay. In the case of HI Torino, they had no clue how to do it and they decided the night was not paid for (no pts associated with that) they went ahead to charge the card used to guarantee the stay. You can do a search to unearth the thread I started on this ordeal.

Now that was on a non-expired cert.

Imagine if it is an already expired cert... I can only imagine you would have many more hoops than I have to jump thru to clear that.

For those of you intend to use your certs this way, you should get this In Writing to confirm you definitely can do so. Else you have very little recourse if hotel turns around to bill you several months after you checked out with a $0 bill.