Originally Posted by neofung

Chance of upgrade is not affected by time of check-in. However, affect the time you know if you are upgraded or not.

When I flied KIX-HKG, didn't do online check-in and on a redemption Y ticket. Arrived the airport 60 min before departure, the ground agent didn't mention anything when I check in. Yet, I was being called while in the lounge and said I was being upgraded to PEY on an A359.

Another flight from NGO to HKG, I booked PEY and arrived at the airport 2 hours prior departure. The GA said Y was overbooked so I might have chance to upgrade to J. However, she could not confirm at the time I check in.

Once also experienced an instant upgrade from Y to J while check in.

So, just be patient and wait. That is what you can do.