Great comments.

I get that there is no revelation here that somehow something is wrong with the stock X5 design. I don't think for a minute there is. I also know that manufacturers shoot to hit 212 degrees if possible to boil off moisture. BUT, I'm not running the OEM fluid, and I know many here who may have changed aren't either, so my point is anyone can do a quick search of transmission temps vs service life. There's a gazillion charts out there - and my Allison manual came with it's own - and it don't like getting much over 200, high $ synthetic and all. I'll stick with the cooler running temps and see how it goes. And I'll follow up on this every now and then - including a failure. Until then - I personally prefer a lower temp.

Some observations I've made just on my vehicles -

2011 Camaro SS 6-sp auto the trans temp runs 180~190 but will climb with spirited driving (which means all the time if I'm driving)

Class A motorhome w/ 8.1 and 5-sp Allison runs maybe 160 going down the road but will hit 190 on a long summer climb. Pulling a car.

2005 Toyota Tundra - only temp I've had is hitting the pan with an IR thermometer. Was running maybe 160 that day, but was a one time check. It has a stand alone trans cooler from the factory as part of towing package.