Our fill TA is usually 120. My PH constantly goes up and because I try to keep it at 7.4 in our AZ climate (sun, dust, wind) + have SWG, I use quite a bit of acid in summer so my TA falls to 60-70.
I do not dispense acid manually anymore, I have Pentair IntelliChem which also has a limit of how much it dispenses at once and how often (mixing time - 1 hour). I hear the pump working and dispensing pretty much every hour in order to keep PH at 7.4.
First time in my life I had to use baking soda to raise my TA to 90, but it seems in a week or so it dropped back to 70. Running around the pool with a baking soda is way better than with an acid, but I could not find any consistent info on what level of TA is acceptable for an established pebble tech pool and at which point I have to worry about a light corrosion, motor corrosion, etc. Does CYA affect TA somehow?
We also have very hard water and high calcium level. I read somewhere that when your calcium is very low or high, it is difficult to balance PH. There is nothing I can do about out fill water unless I decide to invest into a softener just for the pool.