Kaint hep m'sef w'this 'n! Brake jobs, especially rotors, are a deliciously easy method of running up the bill for a less than scrupulous shop. Industry groups have lobbied many states to include rotor thickness into inspectons and mandating replacement if rotor thickness is less than an exceedingly conservative wear limit. Realize this engineering decision is made by the brake vendor to the OEM customer with the attendant liability of a phalanx of ambulance chasers salavating in the wings. Compute the maximum performance of the brakes in extreme conditions and if a tiny amount of rotor mass will cause the heat dissapation to be reduced enough to allow the fluid boil to be effected by a calculateable amount, then that's the limit. In real world situations you can't find a hill long enough with the car loaded heavy enough on a hot enough day to matter one whit. You might also check out the travel of the piston possible with the rotor thinned about 4 times the max allowable and the pads worn to the backing etc and find a large margin of safety designed into the bore depth. There is almost no way a rotor can wear beyond Real limits in less than about 200K, especially on an Insight! The shops in states that have these mandates, like Utah, sell a lot of rotors because most folks haven't a clue and once the brakes/safety card is played the discussion ends with your credit card. But it's just money, and the rotors are nearly all recycled so think of all the jobs you save with your generosity. BTW whenever I run a pad to the backing, I just hang new pads and let them buff the rotor smooth. Sure you will have shorter mileage from those pads, but that is cheap compared to a rotor change for no reason. Hanging new pads takes very little time and keeping the fluid and caliper in good shape is way more important. The brakes will match up in very few miles and don't worry about any ridges etc as that is just a tiny bit more lining area! Nervous Nellies disregard all of the above, as I only have 2mil miles driving over the last 50 years this year, and have worked on cars for 45 years, so my understanding of these issues may not be as up to date as a Trained Service Writer. But then I don't get a vig on service I write either....