Originally Posted by LTN Phobia

I have had them changed (reliably and successfully) changed at the lounge a number of times now. They had nothing to do with upgrades but I wanted to credit different sectors to different programmes for various reasons and I decided that the lounge was probably a good place for it as it was quiet.

As the OP is AA Plat I assume he will be using the lounge, so it may be better to have it done at the lounge, unless he chooses the option to carry on trying for an upgrade until he gets to the gate.