Jimm 1/26/2013The short time period of six months is not long - how many miles are in these six months? Second question, were the brake rotors replacement as equal or better quality than the original equipment (OEM) type? If not, then at the next brake rotor replacement - make sure the brand and type is equal or better than the OEM type that was originally installed on the vehicle when new.
Generally, the brake rotors should last a lot longer than the brake pads - they do not usually have to be replaced as frequently. Have you checked the brake calipers - to make sure the piston is fully retracting - and not causing excess wear or drag on the brake pads - which would cause the rotors to warp due to the heat / friction build-up?
Try the many on-line auto parts sources; such as, www.autopartswarehouse.com or www.rockauto.com for the replacement parts.
Check the 'How-To-Guides' feature on the AutoMD website for specific steps to inspect and replace the brake rotors and components.
rick 1/26/2013Yes they should have . But if the rotors are warping that fast there is something else going on . Could be the calipers are hanging up and this would cause the problem .