my .02 worth, regular maintainance
will most likely prolong life.
Changing the fluid and filter can't hurt.
I had an american car some time ago with a trans that was never serviced cuz a trans mech. told me that particular unit was best left alone cuz it may leak after a service.
Well at 127K miles it was fine. I donated the car.
Usually it is recommended not to overfill a trans.
good luck
I used to have a '76 240D. Fun! baby blue.

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1979 300D
133K miles
1989 300SE
1995 C280