Hey Catnip,
For your reference, my pool is just under 20,000 gal and I run a 60 series cell in the DIG-220. I use power level 1, 8-10 hours of pump run time in the summer, and maintain a FC level of 4-6 (cya of 80 last year) at an output level of 15-25%. Hopefully that translates into longer cell life.

My CYA level is around 40 this year, so I'll see what effect that has on cell output etc.