Despite being the motorcycle system that prevents we bikers from meeting our maker, many bikers seem to gloss over this most important if less glamorous part of their two wheeled steed. Brake fluid is hygroscopic ie it absorbs water, which is good, but it can only hold so much before the water starts to attack the braking components themselves. If there is too high an water content in the fluid under braking the water can boil causing a catastrophic failure just when it is most needed. Brake fluid should be changed at least every other year.
Another fact that few seem to know is that the rubber brake lines fitted by most manufacturers for cost reduction are design to be changed every four years. It is usually cheaper to change the lines for stainless steel braided lines from the likes of Hel Performance which have a lifetime warranty and will also improve the braking efficiency. Never cut corners with brakes - your very life depends on them!