[racer_d]

Remember some maintenance items are TIME sensative, not just mileage sensative. You have given no indication to the number of miles per year you put on or how long it would take accrue the next "20K miles" - 1 year? 5 years? For instance, an item like brake fluid is to be flushed every 2 years. Oil changes either 1 every x miles or 1 per year. As to what "they do", it is spelled out in both the owners manual and should have been spelled out on the receipt they gave you. Also realize that Porsche has both 15K mile service and 30K mile services. Others are done at maybe 60K miles (say,serpantine belt for instance).