But then again how many pedal bodies have you been thru??
I've been running JC/PCs exclusively for a year and a half. I do a lot of pedal grinds (lucees, feebs, butchers, cranks, etc) pretty sloppy and end up replacing the bodies every four to six months. Sometimes sooner, but usually not. I usually keep the spares for just the grind side as I've kept the original tops on both pedals. I'll usually switch out the bottoms pretty early compared to most other people, but I like not grinding through allen heads.
Speaking of which, I put pins on the outside of my grind side of those pedals so that the metal slows down the rate of wear on the plastic. Got the idea on here. It helps keep me from going through the heads of pins that I actually do care about for taking sides apart.
In terms of plastic peg replacement schedule, I'll usually go through two sleeves on my back pleg before I start telling myself my pedals are looking worthy of a switch. Then I put it off for a month or something because mehhh.