Well, I don't know if my thoughts are worth much, but my observations from this site and my personal experience suggests that they can go out between 90,000 and 120,000 miles.
There are probably some that may go much longer, but I think you'd have to be lucky.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".