Totally agree. Do them both at the same time. It's a BMW thing, don't know why. I have a new set of Axxis Deluxe in my 740il for two weeks now, a world of difference. Braking performance is about the same. I have been staying with the OEM brakes on my X because it's still under warranty and it's for free. So I am living with the brake dust for the time being. Welcome to the X5 family!