Originally Posted by
quinella66
I believe the FNA expiration is a deadline to book with it, not to consume it. What happens if you book FNA, but its expiration date passes while your reservation is still there (future) and you need to cancel or change it? Will your FNA automatically expire or can you rebook it somehow?
Unfortunately that is not correct. You need to stay before the expiration date of the FNA, not just book. This from section 5 of the linked help file:
"The Free Night Award will not expire before the Check-In Date of the Reservation"
https://help.marriott.com/s/article/Article-33946