I run late April to October and I have a similar experience, except with CalHypo... I use that stuff for my opening slam and chlorination for about 6 weeks. By that time, my calcium is right where I want it and I switch to LC. My calcium is usually low on open due to partial drain/ refill from closing and soft tap water.
I started doing this last year when I realized it was kind of dumb to buy separate calcium, but I was surprised at first by how quickly my CH went up. I've recruited 2 of my neighbors into the cult of TFP, and they now do the same and save $80 each every year on calcium vs getting it along with the chlorine we need anyway. Round about March we start shopping for the best price on a case of 70% calhypo shock, and each buy one. If we can get a bulk discount, we just split it among us. Maybe next year we will split 3 ways on a 50lb tub.