Surprising the response here regarding the operational safety aspect in regards to brake system maintenance. When brake fluid fails -it gives no warning at all - one push on the brake pedal it works and the next push the pedal drops to the floor.
No matter what has been posted here -brake fluid does need to be changed on modern vehicles, too. Operating environment has a great impact on the life time of brake fluid. Brake fluid life is longer in areas of low humidity and or low moisture. Example the desert SW.
Tow vehicles subject the brake fluid to much higher heat and longer use cycles than a grocery getting vehicle.
ABS components fail from contaminated (dirt/moisture) fluid easily. Price out these components - it is much cheaper to flush the fluid periodically.