Beaner has over 100,000 miles on his car - bought it at about 80,000. You might PM him and see what he has found out.
He does not appear to hesitate to jump into his car and set out on 1,000 mile trips, either.

I do know that I have read that MB says that the trans fluid is to be changed at something like 60,000 miles ... but THEN they go on to say that, after that service, the transmission is "good for the life of the car". I am not sure what to make of that comment, as many cars can go 200,000 or more.

There are threads about changing the plugs - does not sound like a fun job for about the last 5 or 6 plugs!

My XF is not the first thing I've driven with two plugs per cylinder... My Ford Ranger holds only 5 quarts of oil, but it's four cylinder engine has two mags and 8 plugs.