W220 (2001 S430) balljoint lifespan
 

In March 2011 (200,000 mi.), my S430 needed a new left lower balljoint that the dealer installed. Today (at 236,000 miles) the dealer tells me I need a new one. They didn't say anything about obvious damage. I agree with the diagnosis (I've heard bad balljoints before), but I'm astounded that one can go bad so quickly. The right side was done the year before, and seems to be fine.

Can a non-defective balljoint go bad that quickly (no accidents, etc.)?

if the boot of the joint gets compromised a new joint can be scrap metal in less than 5000 miles if driven in rain.

I for one am going to install zerk fittings on my cars ball joints, so I can feed it new grease properly every year.

Chinese parts installed?

I doubt the dealer would install a chinese sourced ball joint.

The invoice says they installed 211-330-04-35 ($82). I have no doubt that the dealer installed a bonafide MB part. I'll have to ask them what they think happened - but they did say that a good balljoint can wear out that quickly.

that can happen if you drive on rut roads, or drive 10,000 miles with a bad tyre that literally hops, or the joint was dry etc.

maybe MB quality has dwindled.