Changing brake fluid, general

When should the fluid be changed? 

It is recommended that brake fluid is changed every other year. In the event of heavy and frequent braking, such as mountain driving or in tropical climates with high humidity, the brake fluid must be changed every year.

Why change? 

The brake fluid is hydroscopic, i. e. the fluid absorbs water molecules from the air. This occurs via the brake hoses and the brake fluid reservoir, which is made of rubber and plastic, and is not impervious to water molecules.

High water content lowers the brake fluid's boiling point greatly, and causes corrosion in the brake system.

This damages the brake system, and reduces the braking effect.