Tried to extend a free night certificate that expires on Dec 25th, for a booking on Jan 14th.
Agent did some investigation, then advised that they can extend the certificate (didn't specify for how long, but said that it could be done for my dates), so seems like 2-3 weeks of extension is doable.
However, they said that the extension could only be done closer to the expiration of the certificate, if I call in anytime from 2 weeks prior to 2 weeks after the expiration (so sometime in December or January, which is ~6 months from now). They were not able to make my booking at this time with the certificate. They had me instead make a booking in cash, that I should then call in to basically have the agent rework the bookings. Upon my questioning them, this would effectively be cancelling the cash booking and then booking an award booking with the free night. I brought up that sometimes rooms cancelled don't always go back into inventory. They said that this is technically a risk but they almost always go back to being available (again... we know that's not always the case at properties the WA Maldives or Conrad Bora Bora. I'm targeting Zemi Beach House, and I haven't seen that type of stuff with their inventory, so I was slightly less concerned). In any event, I opted to make a points booking for that night, that I will then cancel and hope goes back into inventory to allow me to use the then-renewed certificate. From my discussions with them, they were adamant from the notes on my account and the booking that customer service would definitely extend the certificate, but still conceded that there was a small risk that an award night might not be available at that time (even if I pre-booked the room then cancelled).