Pad wear is determined by how often you use the brakes and how hard. City driving is rough on the pads, worse if you park the car for a while and let rust build up on the rotors - the rust can become imbeded in the pad and take a while to be worn off the pad.

It isn't hard to pull a wheel and take a look at the front pads, just make sure you torque lug nuts to 81 lbs. Any pad thinner than 1/8 needs to be replaced sooner rather than later.

The rear pads normally last twice as long as the front, but need to be checked as well.
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My back feels better when I sit in a Volvo seat