Last night I booked a 4 night trip to CUN for my wife and I. I purchased K fare tickets and called and upgraded to G and Z using 4 SWU.

Today my wife has granted permission to extend the trip to 5 nights. Due to logistics I will need to change both the outbound and return flight dates.

I am fairly certain that I can still cancel the flights that I made last night without penalty since it is before midnight. My question is, if I cancel the flights will I loose my SWU or can I have them re-applied to the new flights?