Flying CX for the first time in June. I have enough Asia Miles for an upgrade to J, but currently no award seats are available. Assuming availability, does CX release seats for mile upgrades as the travel date approaches, or do they reserve these for op-ups?

I think CX will be vastly superior to the service I'm accustomed to in the United States, though I am not that excited about the new Y seat...

Thanks in advance for your help.

NSN