If you didn't get the brake pad warning...then the sensor is still "intact". Yes, you could change it, but if you are changing your brake pads BEFORE the warning appeared...then you'd be throwing away a perfectly intact brake pad sensor that can still be used.
And if you did reuse it because you replaced your brake pads prior to receiving the warning...there will be enough material on the new brake pads for thousands of more miles before the pad get's thin enough again to start wearing down to where the sensor would make contact and wear down to trigger the warning.
Just a thought.
