I've had my KW Street Comfort coilovers on about 9 months now including one winter. The other day I noticed the coating on one spring was peeled in a few spots and the metal rusting. There's a one year warranty on their coating. I e-mailed KW last night with my order receipt and pics and today they replied and placed an order for a new one. Quick and easy. It sucks it failed in the first place, but they handled it without hassle.
EDIT: Spring arrived a few days ago, about two weeks to receive like they said it'd take (shipped from Germany).