If you clean the rotors too much then you are working against yourself. After 4500 miles new pads are in order. You won't believe how your power goes back up with new pads (might as well put new cables on too). Check to see if you need new rotors at this point as well. Clean the rotors once very good when you replace the pads then do not touch them after that.
The rotors need to bed in with the new pads - if you keep cleaning them after that they will have less power until the pads rub the surface up again.
I am sure their is a scientific explanation for this about the rotors being filled at a microscopic level with some of the brake pad material that helps in braking but I am not 100% sure.