Aftermarket replacement rotors warp much easier than their OE counterparts. The rust problem is common on both aftermarket and OE. We buy insurance cars which may set a year or more due to negotiations and title snafus. The rotors are often deeply rusted where the pads sit on the rotor for that long and you can really feel it in the pedal. We used to have the local O'Reilly's turn them because they turned them for free for commercial customers. But, the help was so incompetent, that they ruined some rotors, damaged others, broke bits, and finally damaged the bearings in the machine which O'Reilly's decided not to have repaired. We just decided to buy our own machine. $500 for a nice used unit. We don't do a lot of rotors, but now we know they are done right. And don't have to wonder when they will get done.