Just to add my recent experience. Unfortunately, due to a change of job, I no longer travel as much as I used to, so dropped to Lifetime SG last year from WP.
I was booked on a sale premium economy fare, BNE-LAX on 6/6, returning LAX-BNE 12/6 (tonight). I also did not have enough points for an upgrade request either way.
One week out from the first flight, I was offered a bid now upgrade to Business, I offered 15k points plus $800 - offer was accepted about 30 hours out from flight - great flight on the 787.
I was waiting for T-7d for the return flight, Expert Flyer was showing J,C,D,I 9's - no email. I then had this crazy idea - top up points!. I only needed another 15k points, so cost around $500 to purchase, was able to request a classic upgrade award. Anxiously watching the loads - T-48h was at J8 C8 D8 I5. Checked my points balance at T-30h - points deducted - success! Now will be sitting in 1a for the ride back.
Now since the upgrade happened, one of the A380s went tech, so QF 94 and QF93 were both cancelled on the 12th, so all flights from LAX suddenly zeroed out and all seats occupied. Interestingly, only received the text notifying me of the upgrade about an hour ago (T-7h).
So overall, very happy with the result, ended up with 2 quite cheap business class flights.