As CYA increases, so does the half-life of chlorine in the pool. With CYA = 0, the half-life in clear shallow water is as little as 15 minutes!

However, the effective life of chlorine seems to go up as CYA increases, even when you maintain a constant available unstabilized chlorine fraction. For example, a pool with CYA = 20 pm and FC = 1 ppm has approximately the same available unstabilized chlorine as a pool with CYA = 200 ppm and FC = 10 ppm. But reportedly it takes MORE chlorine to maintain the first pool at 1 ppm, than it does the second pool at 10 ppm, assuming equal gallons, loads, sunlight, etc.

That's really something I need to experiment with.