From what I've noticed on other BMW's I've owned the brake monitoring system is accurate to a fault. When I had 1200 miles on my fronts in my E60, I immediately yanked the front wheels, pads and rotors and replaced with Zimmerman rotors and Brembo pads. The front pads were thin on both sides which leads me to believe that the system is accurate in it's reporting. Thats the basis I am using just purely on experience. (granted the E60 is not an E70 but logic dictates that the systems are similar but with german cars that assumption doesnt hold much water)

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2010 X5 3.0 X-drive Titanium Silver/Black
2018 Ford F-150 Platinum Crew
2010 528xi (His)
2017 M2 Manual (His)

Former Headaches:
2008 X5 RIP
2015 M235
2013 135is
2009 535xi Wagon (JUNK)
2007 530xi 6spd CPO Sport (Best Damn Car EVER)
2011 335xi M-sport Coupe 6spd (Sex on Wheels)
2010 550GT "CPO" (Junk)
2012 X5 35d "CPO" (More Junk)
2004 330i ZHP Sedan
2002 325xi Wagon
2000 323i Sedan
1998 M3 Sedan
1992 325i Sedan