I wouldn't say there is a certain time to change the break pads, it depends on the driver of the car. You can always just check the break pad wear from the outside of the front tire. And sometimes you can just tell by the sound you hear when you step on your breaks. As for brake rotors, advanceautosports says to check it every 5-25,000 miles.
read the maitainace manual that came with the car. it should tell you an estimated time to service the brakes.
5-25k miles??? Holy breakriders Batman! In reality, 5-25k seems reasonable. If you are tough on your breaks, the pads will need to be replaced and the rotors machined more frequently.
thanks fellas I just wanted a ruff estimate because I'm planning to to buy rrm pads and rotors when the stocqk ones are done