I'd say...believe it. You're doing something right. Also, if the pool is not being used, there's little to use up the chlorine.

How much water are you circulating? What horse power pump do you have? Perhaps 12 hrs/day is more than necessary? I run my system 6 hrs/day.
But my 20,000 gallon pool gets more than 80 gpm (80 gal/min x 60 min x 6hrs/day = 28,800 gallons of water being circulate per day). More than enough for proper filtration.
I have an SC-48 cell with the Total Control, so I don't really have to adjust the % output. it's automated.
However, in your case, I would reduce the pump run time to get at least one turn over per day, until the temperature increases into the 80's.