I have the exact same issue, and I have a LOT of pad left. I figured maybe it was pad indicators but I looked and the pads look nearly new. I've had this problem on a few vehicles (which were all pretty spendy vehicles to begin with) however, the temporary fix is typically the same. This was something I had to do in my Denali to keep my brakes quiet.
When i first start driving, I ride the breaks from a stop to about 25 mph then back down to nearly a stop again. Don't have to be pressing too hard, but enough pressure that you can feel it resisting. After doing this the brakes are silent for a couple days and then it will come back.
2004 645ci - SOLD