I have 46k miles on my 2010 Versa HB. I had my tires rotated last week and asked the mechanic to check the brake pads. He showed me the front brakes were down to about 20 percent and the back brakes were down to 40 percent. They have a brake pad special deal going until the end of October. Anyway, I said I would probably replace all 4 pads the next oil change in October. How far down can they go before replacing? I thought they make a noise when they are too worn. Should I replace all 4 at the same time? The special seems like a good deal, but I need to ask what type of pads they are and what do others recommend? Thanks.