Originally Posted by Das Benz

I would say around 200,000 mi is a good estimate. My 420sel had 382,000km (237,000mi), before the reverse gave up on the original trans.
My 560sel is still shifting like a champ, but reverse is a bit slower then I would like. Right now it has 362,000km (224,000mi). Then again there's various factors that would affect this. Vehicle weight, driving technique..etc. But its a decent guestimate for anyone jumping into a new-to-them benz purchase.

My buds 91 300e has around 226,000km, trans still feels fresh, and reverse is nice and quick.