I have 4 award cert that expire on Feb 28th. Are you saying I can use them for a reservation that I have already booked in August?
You can apply suite upgrade certificates (I'm not sure about free night awards from the credit card) before they expire to reservations made for after they expire.
However, you will not be allowed to change the reservation or you will lose the certificates.
FWIW - I WAS able to change without losing them. I didn't ask, and customer service didn't volunteer. However, I was only shortening my stay, not changing it.