My 420SEL has 243k miles. Only major repairs have been valve job, catalytic converter and a/c pushbutton unit. Fully expect to go well over 300K with it. Will eventually need paint job thanks to several supermarket dings. Have put new shocks and am thinking about new rear springs, as rear end is showing a hint of drooping. Local MB shop says they have never had to replace rear springs - anyone else replaced theirs?