To answer your question. It all depends on how you drive. The FSS takes into account the length of trip, speed, temperature, etc. If you are like me and do not drive the crossfire except on the weekends and only between April and October then I change the oil before I put it away for the winter. Just a quick aside on the oil. A while back there was a post on the list that listed the USA approved engine oils that meet MB's standards. I thought it was interesting Mobil SuperSyn 0W-30, 5W-30, and 10W-30 DO NOT meet the standard because they break down in visc at high temps. Some on the list say they use these.

My wife's MB has a system like the Xfire and last oil change she drove it a little over 8000 miles between changes. (A service). That car runs on Mobil 0W-40 and a fleece filter. Mostly highway driving and at extremely resonable speed and slow off the line. Hope this helps.