Replacing all the suspension bushings gets expensive fast and it requires some tools and knowledge. If your tires exhibit normal wear and car is handling well why fix something that isn't broken. It's not like a worn bushing will leave stranded out on the road; That's what preventative maintenance is all about. It depends a lot on how the car is run. Do you find yourself on salted roads during the winter, or does it have a life down in the sunny south? Is the car stressed on a race track,? Mercedes makes their equipment to pretty high standards. I recently replaced all the cooling hoses as a preventative maintenance item and when I was done it seemed a waste of money and time; Those hose were all in really good condition. My cars have always been in the deep south or a heated and cool garage. Makes more sense to check those small vacuum hoses behind the auxillary air pump. I did that just the other day and mine are all still pliable. If your suspension arms are rusty and crusty then yes go for some new ones. You will be buying the complete arms, as replacing bushings just isn't worth the little money saved over getting an new arm or link.