A good way of telling whether you need new brakes and rotors is to remove the wheels and look at the rotors and brake pads.
If the brake pads are thin and the rotors have grooves or are getting thin then it's likely you need new rotors and if the brake pads are thin you need new brake pads.
Brake pads also have a metal piece on it that makes contact with the rotor when your brakes are thin enough to need replaced so if you hear a scraping sound coming from one of the wheels then you need to replace the brake pads.
Other signs that you're having brake problems or need new brake pads or rotors is.
Brake Light On.
Squealing, Squeaking or Grinding Noises.
Wobbling, Vibration or Scraping When Braking.
Leaking Fluid.
Spongy or Soft Brake Pedal.
Car Pulling to One Side When Braking.
Burning Smell While Driving.
Bouncing Up and Down When You Stop Short.
If you notice any of these symptoms then you have brake trouble and need to get the brakes checked out and fixed because it can cause more damage to the vehicle and could cause a potentially fatal wreck so never ignore these warning signs.
Brake Pads should last at least 70,000 to 100,000 miles depending on how you drive the vehicle and rotors should last from 100,000 to 200,000 miles also dependent on how you drive the vehicle and use the brakes.