"My bike has just shy of 13,000 miles on it...."
if your rear pads wore down to the metal in only 13,000 miles, I think something is wrong with your rear brake, or you are riding with your toe on the pedal.
Possibly the caliper has been hanging up.
I still have the original front pads on my bike at 30,000 miles, and they are no where near needing replacement
the rear brakes should last 3 to 4 times longer than the front.