Getting your brakes inspected, repaired, or replaced is part of your vehicle's regular maintenance and it is very important. There is no set schedule for getting your brakes worked on, as it varies by vehicle usage. It all depends on where and how you drive your vehicle and the quality/life of your brake pads and rotors. Those who drive more frequently or longer miles will probably need to have their brakes replaced more often than someone who simply drives around town.
There are however signs that your brakes need to be repaired or replaced.