I drive an 06 C 280 4matic and at 38,000 miles I had the transmission fluid (to include the torque converter) and filter changed. The car shifts much quicker and crisper now. If you look in the manual, you will see that the service schedule calls for trans and differential service at 39,000 miles. For those of us who can't afford to trade every 2-3 years and need our cars to last into 3 digit mileage, DON'T BE CHEAP, get the drivetrain serviced sooner rather than later. The "lifetime fill" propaganda was invented by marketing types who were trying to dispel theperception (which happens to be true) that German cars are more maintenence intensive than their Japanese and American counterparts. The technical editor for Mercedes Star says to change the fluid and filter every 30-40,000 miles. If you still don't think you need to do this, just spend time reading all the posts about transmission problems.