Hi all, not finding the asnwers to my (burning) question. So here it goes:

I have flown the first of 4 sectors. flying in PY booked in R. So can upgrade to J class (U). I am being told its 30k miles for that (HKG-BCN-HKG). As I am waiting on a partner to book their flights, I am not certain I will be wanting the upgrade, as they may not get the business class ticket.

If I upgrade now (via website) and then later decide I actually want to go back to PY, and not use the upgrade is that:
- possible?
- will I loose the miles?

Flight is about 6 weeks away, 10 empty seats on the A350 in J.