I have owned my W168 for a little over 5 years now, and have done all the servicing (and more!) myself. I have replaced all the B service specific items more than once during my ownership. I tend to base my service schedule on the time limits given by MB and also on what I feel that the car needs (preventative maintenance). I had to reset the assyst today and it occurred to me that in all this time the car has never requested a B service??