Dorman actually did report a problem with their manufacturing line on the elbows a while back and they do stand behind their lifetime warranty.
Something to consider though. These should be installed in clean (no ridges from the previous elbow) tensioner/lim/timing cover holes. Using a lubricant on the o-rings. I prefer vasoline (cheap and in the toolbox) or oil. When tightening the tensioner to the head of the motor, wiggle the top elbow to ensure it does not get bound. Even when the bolts are fully tightened, it should have a little play. If that doesn't happen the elbow tends to deform with heat and leak.
