Dave, it's difficult to say how long or how many miles the brake pads will last before damaging the rotors without knowing your driving habits. It would seem that you do a considerable amount of highway driving ... based on that I would say up to 2,000 miles. Obviously as soon as you replace the brake pads the cycle starts on the new brake pads so it's a good idea to maxmize the wear on the existing brake pads. However, if you're a procrastinator it may be wise to change the brake pads sooner rather than later.

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Fred Hoelzle