Is there a certain window of time

[Tredge]

I'm also dealing with a high TA.

Are you also adding CYA? I think this will make it look like your TA and PH are going up when they are not.

Aerating actually causes your PH to go up. The only way Aerating will work is to keep adding Acid....if you can keep the PH low for a period of time then the TA WILL drop. It can take weeks.

Shoot for a constant PH of 7.0 (6.8 for a plaster pool) and watch your TA closely. When it starts to drop it will drop significantly.
Also remember that TA isnt a thing, its a measurement of the waters resistance to changing PH. It can go back up and in my experience will bounce around a little while you are trying to stabalize the PH.

This is all from info I've gleamed out of this forum, I'm still working on it myself.