Does KrisFlyer upgrade availability come and go, or once it's gone it's gone?

Hi gang
I have purchased an economy standard fare (W Class) from MEL - SIN - LHR with Singapore Airlines. I was told hours before purchasing the ticket that there was availability to upgrade to Premium Economy on both legs at a cost of 63,000 points (which I have).
Once I purchased the ticket, I logged into my account only to find that there was only availability on the MEL - SIN leg at a cost of 34,000 points.
My questions is:
Do I lock in the upgrade available now, or roll the dice and wait to see if availability comes up for both legs. If I lock in MEL - SIN now and the SIN - LHR comes up, then buying the upgrades seperately will cost me 81,500 miles as opposed to the 63,000 miles for buy both legs together.
Once availability is listed as unavailable, is it likely that this will open up down the track to available?
Many thanks

Hi timilla,

Try calling Krisflyer and tell your agent you want to upgrade both flights. If the agent says only MEL leg available, ask the agent whether you could confirm the upgrade for the MEL leg while waitlisting for the upgrade on the 2nd leg. If allowed, they should allow it all under the same upgrade (1 instead of 2 upgrades).

They might charge you the fee for doing it over the phone, try and ask them nicely whether they can waive it as you weren’t able to do it one the website.

Singapore airlines waitlist is a mystery. You could keep calling them now and then to ask them for a “chaser”. To see whether they can push through your waitlist.

Good luck.