I drive about 5k miles per year but always get the annual service. I use a local independent garage that specializes in Mercedes. I just got the Service B interval. It’s effectively the same as Service A but with a brake flush, and you might need a cabin filter. The difference is that my garage actually looks to see if you need the filter replaced versus just charging you for the full Service B. My experience at a Mercedes dealer for my rear diff oil change was less than ideal (and overpriced) so I researched and found a reputable garage. I have a 63S, and a Service A is under $200, plus a brake flush for under $150. Two dealers quoted my over $500 for a Service B, so about 30% less, but with a personal touch.