Possibly a dumb question, but we have multiple overseas trips booked right now. I plan to cancel them in a rolling fashion, as who knows what happens to the trips in the fall at this point (not high hopes, but...). My question is, I'm actually fine receiving an e-credit for the flights I know I won't be able to do, but will I be able to combine e-credits for say one more expensive flight later instead of the 2-3 flights I have booked now?