One other thing to look at–the brake hoses. We learned the hard way w our 89 Plymouth Voyager. We had already replaced a proportioning valve and the master cylinder. I heard a scraping noise and thought it was just brake pads although we are generally proactive on maintenance and repairs. Took it to a brake place and they replaced nearly everything including the master cylinder. Then it leaked right away and the replacement leaked too. So they got a heavy duty one that held (5th one in a short period of time). The brakes never felt really good and the minivan had no power. We drove it little after we got another vehicle. Let it sit for a few years after I went out and found I had no brakes and fluid was leaked out of the master cylinder. Recently, we decided to get the brakes fixed, thinking maybe a wheel cylinder was leaking. Well, there was a scraping sound when the tow truck pulled it up. Turns out our rotors were all grooved and the calipers were frozen. The brake hoses were deteriorated inside so the brake fluid was held up within them. Had to replace them. Now that we have new brake hoses, we expect master cylinder and the new rotors to last. Brakes feel good now.