So if the TA settles to some amount where acid addition isn't lowering it, then that means that either the amount of TA being added from evaporation and refill is matching that lowered from the acid addition or that the pH rise is not from carbon dioxide outgassing (or a combination of these two effects). Another source of pH rise in SWCG pools is from undissolved chlorine gas outgassing and when acid is added to compensate for that there is no net change in TA.
Rather than have a large pH range, if you use 50 ppm Borates then the pH won't rise as quickly. You may still use about the same amount of acid over time, but could add it less frequently.