Just a data point - I was told by a CSR at one point that the reservation had to be made before the annual night certificate expires, but this was incorrect. The stay has to OCCUR before the cert expires. In my case I had a cert expiring 7/31 and made a reservation for next March. Oddly they never said anything about the expiration date but when I tried to add another night from my wife's certs they said the certs would be expired and we couldn't use any of them. Unfortunately that meant a certificate went to waste.