Some knowledgeable people say trans fluid / filter changes every 15 thousand miles - that seems so often in my opinion. If your putting big miles in a short time, fluid filter change every fifty thousand miles is maybe more affordable. But at least your on the right track with doing a trans/fluid change in the 10 to 15 thousand mile range with the idea of removing break in particles from the trans.
Also do you come to a COMPLETE stop when shifting from reverse to drive?
In the U.S. Mercedes rebuilt transmissions are a good deal, not cheap but piece of mind.