New 06 X5 4.4 Owner in Austin

[RickX5]

Greetings everyone, this board has been super valuable in helping me decide what to buy and what to look for in an X5. I ended up with a hail damaged vehicle with 36,000 miles. Since the factory warranty expires at 50K/ end of this year I intend to perform a more aggressive maintenance schedule that the factory reccomends. i.e. change the oil every 10K, change the tranny oil, diferential oil periodically etc.

A quick question on the tranny fluid...
Rather than the labor intensive process that changes ALL the oil is there a down side to just draining what will come out by removing the fill and drain plugs then adding fluid to refill to the proper level?
It seems if we do this annually it would keep the fluid fresh and maintain the additives.
Thanks
Rick