I know this thread was resurrected from the depths of history, but it does bring up an interesting point. My experience with Wellman's was not a happy one, Replaced all 8 at one time, within 6 weeks 3 of them had burned out. Don't know if I got a bad batch or what, but the problem certainly wasn't advanced timing! I've had one set of ZD-9's in for a year and a half now and they all work flawlessly...