I had to replace the brakes on my wife's vehicle EVERY SINGLE YEAR. You read that right. She traveled a decent bit for work and averaged about 50k miles a year. The point im trying to make is the brake hardware in that system was polished clean and new hi temp synthetic grease used every time. The brakes were flushed and bled every year. She had a caliper hang up on her out of the blue at 250k miles. It doesn't matter what practices or how perfect you try to make everything work, sometimes things just give up the ghost. The car had a new hose and caliper installed and got moved down the road at 274k miles.