Drain and fill will NOT break the trans. I would stick to a 30k mile schedule for drain and fill. The trans fluid runs through a heat exchanger on the back of the coolant radiator and I think that is a bit high of a temp for a trans. My 5HP24 has done about 30 k miles since I refurbed it and the fluid coming out did not look pretty. hence my suggestion for 30k intervals.

My trans failed after the torq conv broke and sent shrapnel in to the trans, no telling when something like that happens.

Enjoy the car!

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2003 4.4i black ext./black int./black headliner (kid's runabout)
2014 535d X-drive, M package, silver/black interior

Sold but not forgotten:
2009 E70 35d, black ext./black int./black headliner (sold 2021)
2006 4.8iS Le Mans blue/cream int./black headliner, SOLD in 2012 sadly...

Other hardware:
2015 Cayenne S (wife's new DD and definitely wroooommmmm)
2016 Tundra 1794 edition crew cab, luxo hauler
2005 Tundra crew cab, weekend hauler. Sold after 150k very happy miles.