The transmissions on our X5's should be serviced well before the 100K suggested mark. The fluid is not meant to be used for that long period of time. I think the reason for tranny failures is due to the lack of fluid and filter changes. I just finished servicing my transmission and the fluid was near black. I've only driven the car for a day since and everything feels better. Its as if the transmission has new life. I've got almost 82k on my x5 and i'm sure glad I serviced it. Sometime within the next week, I do plan to do one quick drain and refill to hopefully drain out more of the old fluid which was still locked in the torque converter.