This is pretty far in the future (3/25), however everyone on here has good advice:

Flying 881/882 ORD-BKK (with a connection into ORD) in March on vacation, applied the SWUs and the return on 882 cleared immediately. Day before making the purchase UAL indicated upgrades were clearing, when I applied the SWU, the outbound waitlisted for all of 881. I checked the seat map last night and the entire main deck, aft C cabin is full, leaving 1/2 upper deck and 1/2 main deck forward C available. Traveling with Mrs. PLTHOO, therefore I don't want to risk not making the upgrade or waiting to the week of....I know it is still early.

I checked the 12:50 777 flight ORD-NRT and C is wide open, as is 881 NRT-BKK. Would I be able to change the ORD-NRT flight to the 777 without a fee? How does this affect the applied SWU? Am I just getting uneasy for no reason? Why is the entire aft C cabin full (all seats) this early?

I am also having the SWU applied to my connection into ORD, therefore I don't want to miss the upgrade on that flight (limited F cabin) because of the ORD-NRT waiting to clear so late.

As always, thank you for your advice.