how often should i have my brakes replaced?

it will vary from car to car,driving conditions,foot on brake,foot on gas pedal,hard braking.if good brakes installed correctly and rotors in good shape,they could last a long time.if you feel any difference in the pedal or they make any noise,have them checked/inspected.i have a 2000 f-150 and have over 70,000 miles on mine and still good.