If I recall correctly, the M-B's official stance on the 722.6 it that you change the fluid once at 39,000 miles (60,000 km) and then it is sealed for life. Considering how much they cost to replace (don't ask me how I know!), I will be changing the fluid and filter every 40,000 miles or so. It's cheap insurance if you ask me!

__________________
"It's not about how fast you can go, but how well you can go fast."

Bob in Richmond

'97 S320 (LWB), Ruby Red Metallic, 73k miles
'97 S420V, Smoke Silver Metallic, 155k miles