Depends on mileage, is it recommended at 30k or 60k? Likely 30k and the reason it is recommended is that brake fluid is vented to the air because it expands when heated during brake operation, because is vented it will absorb moisture from the air and then the boiling point will lower and can cause brake fade especially when coming down a pass and may be riding the brakes and not letting them cool down. Loss of pedal pressure in this instance can be frightening. Moisture inside the brake fluid can accelerate the brakedown of internals in the brake system. Fluid may still look good but that is why it is recommended so brake system has a chance to remain in top shape. I personally feel the most important system on any vehicle is the brakes. But of course it is your call. By the way, if you use synthetic brake fluid it does not absorb moisture.