Yesterday I booked a flight using FFCs expiring in the summer for a flight in the spring, immediately changing it to a flight of equal cost in the fall that I actually wanted. Today, I noticed a price drop in the flight I booked. When I changed the flight to take advantage of the price drop, the FFC it gave has an expiration of 1/22/26 (which I tested to make sure it was actually valid through at least the end of the currently available schedule) even though all the FFCs I used for the original flight had a spring expiration. So, tentatively hoping that the previous trick of extending the date of FFC's works again.