Yah...balljoints should last 100,000 miles or more. But that "usually" they said means if the boot isn't torn, if it's street-driven only and never hits a pothole, if......you get the point.

With torn boots, water and dirt can get in and contaminate the grease or cause rusting, or the grease can dry out, or......anyhoo it'll cause accelerated wear on the joint shortening its lifespan.

I'd get a little more insistent with em about getting them replaced. Those are sealed balljoints with no grease fitting right? No way to lubricate them means no way to maintain them so the only option is to have em replaced. Be ornery about it. If you have to, take it to the level that the service manager will start looking for a hiding spot whenever he sees you walk in the shop. They'll change em.