Originally Posted by Benz Dr.

The 220SEb is a 5 main bearing engine. Most are worn out at 100K but many will run longer than that. The head will wear out about twice as fast as the bottom end so a valve job half way though can get you to the 140K mark but not much beyond that.
Typical cylinder wear is about .001 per 20,000 miles. You are allowed .003 wear before it starts to get worn out but I've seen .007 and they will still run OK. I once had a 230SL come in with .015 cylinder wear that barely ran. I had to bore it out to max oversize all in one deal. The guy I bought the pistons from said it was impossible for it to even run but it did. No cylinder was more than 110 PSI and every bearing was nothing more than copper shells.