The machine is a very important component of the vehicle brake fluid, exchange should be conducted every two years. Reason, that no matter how well the system is sealed, the liquid it absorbs water and thereby reducing the boiling point. If the brake fluid boils, typically at higher stress, reduce the braking, or may stop completely. It is then, when it is most needed.
Different standards exist, The best known is probably the DOT (Department of Transportation) regulations. These parameters are prescribed for different minimum requirements for different categories. These mostly relate to the viscosity and boiling point.