[aero901]

Sway bar links typically go bad when the rubber sealing boots fail/get damaged, let water in, contaminates the internal grease, and allow rust to form around the pivots. Usually results in a clunking noise when going over uneven bumps in the road as the joint surfaces wear from the lack of lubrication. I've installed cheap (ungreaseable) links before which have only lasted 1-2 years so it's definitely possible they may need to be replaced often if regularly used on rough roads. The greaseable links (Moog), in theory, will last much longer if grease is added regularly. I add a pump of waterproof marine grease to mine twice a year (car lives in the rust belt) and have had them installed for about 2 years now with no issues.