Some advocate leaving the fluid alone, others do not.

I go off this basis -- in South Africa they have Taxi's with 722.6's in them with 500k miles on them, who have changed the fluid every 60k according to schedule. And that is not just one example, there are many. There is a huge thread about this over on mbworld....

I would bet money there are zero original fluid 722.6's who have made it to 500k.

I changed the fluid on our 2002 CLK320 at 105k original fluid according to fluid analysis estimations, and have had zero issues and feel way more comfortable than wondering.
If you do change the fluid, USE THE CORRECT one. Do not substitute.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k