There are specifications of all brakes(disc and drums)that say when to replace for safety.Its usually better to turn then(with brake machine) to make them completely smooth again.They measure them to make sure not too thin.
__________________ 2006 Gt Premium coupe,automatic,white with red Shelby stripes,18 in.wheels,seq lites,plem. cover,Rouse hood scoop and flowmasters,Steeda strut brace,Steeda polished stainless fuse and radiator covers,rear camera(Boyo tag cam)thru Crimestopper rear mirror.Ford molded mud flaps,Silverhorse polished billet fuel door,and chrome console trim. | 
Rotors and brakecompnents 
