Famous last words. I have never had a pair of rear pads wear out first. Period.

My X5 also says that the rears will wear out first. I doubt it. It's an educated guess based on driving style, blah, blah. Only as good as the algorithm written by the programmer.

Look through the rim and keep an eye on them. If you need to pull a wheel ever now and then. That's what I do. I have never replaced a wear sensor nor have I relied on one to tell me when my brakes are worn.