The pads have a electronic wear indicator. There's a sacrificial contact mounted to the base of the brake pad.
when it wears out it opens up the normally closed circuit and then a light should come on.. also the pad material is riveted on to the base plates with brass rivets. If you get a brassy appearance on the rotors you know the pads are starting to get thin But they're not done at that time. The brass rivets are meant to wear and not damage the rotors.
Conventional brake pads use steel rivets and as some of you have probably seen on pads that wear to thin the rivets grind into the steel rotors which usually leads to resurfacing of the steel rotor. The brass rivets prevent any catastrophic damage to one of these expensive CC rotors..
Weighing rotors is just one component of monitoring the brake componets. . you have to monitor the rotors weight and the thickness. And in reality the rotor can maintain its thickness but lose weight by cooking out the binding material
The rotor would need to be replaced if you got down to that minimum weight as listed . I did an extensive study on the system that I have on my 06 car.
I weighed the rotors new and they allow approximately 30 grams of weight loss before it needs to be replaced
Living with the carbon brakes on my 06. For about 8 years. . I'm on my third set of front pads on the 06. No rotor thickness loss or no weight loss..
The rotors on the new GT are updated material. I don't think anyone will ever wear them out unless they're tracking the car every weekend...