You should flush the brake fluid in your car at least once a year to maintain peak performance. This is important because proper braking performance is crucial to safety.
Brake fluid is affected by moisture and the hygroscopic property of this liquid will make it vulnerable to moisture content. This is the reason why the brake fluid reservoir in your car is sealed tight. Moisture and water inside the braking system would greatly reduce heat resistance under extreme use and would lower the boiling point of the fluid. Remember that your brakes could get very hot even under light use or short journeys and relies on the excellent heat resistant properties of the brake fluid and brake pads. If the brake fluid is contaminated by water, it will be susceptible to boil and eventually evaporate. This will lead to loss of braking power and a potential accident on the road.
Moisture will corrode metal parts in the brake system and would lead to rust formation, thereby decreasing the service life and efficiency of the various parts and components in the braking system. This is why it is imperative to undergo brake flushing at least once a year and use high quality DOT 3 or DOT 4 brake fluid as recommended by the manufacturer. Consult a trustworthy mechanic for a brake flush service and have your entire braking system checked for proper specifications. Remember to wipe the brake fluid reservoir cap with a clean towel before and after replenishment to ensure that dirt and moisture will not enter the reservoir.