Originally Posted by LVP

Light would come on for pads that are worn so low the sensor gets worn off. Then you replace pads and sensor. As for rotor thickness, I'd let them get right to the minimum if they aren't warped.

I have the cross drilled, slotted ECS rotors. They look great and have a great coating (why I bought them) and the price point is good. But mine developed a nice warp/vibration about 5,000km in. I'm just running them out and will likely source a Zimmerman or original BMW coated rotor for the next set. The coating is important and I've had good luck with Zimmerman on all my cars (street and track).