Wait for brakes light ON to change brake pads, bad idea ? is it too late already if warning lights turns ON ?

[Benzw205]

hello,

 

is it true that if you wait that your brake light turns ON to change your brake pads, it's already too late, and then you will also have to change the brake pads sensors that alerts you when your pads are dead ?

 

Also, I have been told that you do not always need to change your brake discs, you can "fix" them, kind of renovate to bring them back to "new", do you recommend it ?

 

Thank you so much for your ideas.

[dagger]

Once you get the warning light on its due to the pads wearing down to the sensor and you are left with about 10%.
Sensors are cheap, couple of bucks only.

Rotors can be skimmed couple of times (2-3 times depending how uneven the rotors are), but up to a minimum thickness of the rotor (usually down 2mm from original thickness, some may only be 1.5mm).
Recommendation is to change the rotors once you have skimmed the rotors twice.