My personal preference is to buy cheap organics for rear and replace them often. While I understand importance of the front brake stated above and use it accordingly, my rear also gets used a lot--dragged to help in stop and go traffic and some low speed maneuvers. I use more rear (and less front) when it's raining (because I found out the hard way that although a rear wheel skid is dangerous, a front wheel skid, such as occurs when you hit wet oil, is so very much worse). I also use the rear on dirt, gravel, and other less than perfect surfaces (sand sprinkled pavement, etc) for similar reasons. And for normal dry pavement I use both brakes because though the front will stop it just fine on it's own, it keeps me in the practice of using both, so it comes automatically for emergency quick stops. All of this wears out rear pads. I go through a set or two every year.