For future reference, what happens when one is starting from East Coast rather than West Coast, so a transcon before flying trans-PAC. Does one find out whether they will have the upgrade trans-PAC at the outset of their trip or might they not know until they get to their gateway city?

I would like to go sometime, but find the prospect of a 20K RT daunting under the best of circumstances (e.g., C or F), and fearsome in Y. What are the chances I would spend money on an upgradeable fare (W rather than S or T) then not be able to use the SWU to BKK, or have the SWU taken for only part of the way rather than all segments? If wasn't going to see the upgrade, would consider taking the $250(?) cancellation fee and going back home, that is if hadn't commenced trip already.