All I know is, that I don't trust my older benz on a route longer than 50 miles or anything outside my state. reason is, i know well from the posts here and experience that the benz will give up any time and would have to be towed back to the mechanic. therefore as a rule of thumb i drive it only on the local routes. I don't even let anyone else in my family drive it. reason, i dont want anyone else stuck on the side of the road even on a local route. so whether or not the mercedes is built like a tank to last, that tank is no good for me when i can't drive the tank on long routes without having to worry every second about it 'staying' on the road.
as an example, read the most recent post by haasman where his w124 has left his wife stranded. and i can tell for sure that his car is one example where he's maintained it well beyond what the manufacture would call for in terms of regular maintenance.

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Whether you think you can or cannot, Either way you're right!. by Henry Ford.