I've been using the same Camp Turbochest for close to three years now (just about to replace it due to worn teeth), but there's no rust on the cam at all - a tiny bit on the back spring, but that's it. Most of the cam is still black, to be honest, and it's had some serious abuse. My only tiny gripe with the Turbochest is that if you're doing wide rebelays to the right, the rope can sometimes slide out of the top roller, but I think it's more a case of me not adapting well to a new body shape than any major fault with the design.
Incidentally, three years is amazingly good value - I was getting through a new Croll every year in comparison, and that was always from worn teeth and an enlarging attachment hole, and in one case a v-shaped groove at the top. I've been using a Petzl Basic hand-jammer for one year, and the teeth are wearing flat already. Again. So I might see if I can get hold of the Camp Solo 2 instead and see if that too has a longer-lasting cam.