wow...I rode around with no brakes for about two months because I thought it was silly to replace them after only a week. I've actually replaced a couple sets after about three miles. Taking big downhills at high speeds with a looming red light is bad for them.
But from what it sounds like I might not have needed too. They had looked just like the rim when I took them off, either from catching on fire or simply "brake dust", I don't know. But can they be cleaned or do you have to replace them when they're hard and metallic looking if you want to stop?