Brake pad life depends on several things. Use of the vehicle (towing a trailer, always driven fully laden), type of roads the vehicle is driven on and the driver's braking habits. Brake pads also are made from different materials some last longer some last shorter. Also in general vehicles automatic transmission cars will wear out brake pads quicker because in a manual transmission vehicle you tend to downshift rather than pressing the brakes.
Front brake pads usually last 30,000 miles rear 50,000 miles but each driver is different. I got 60,000 out of my Toyota front brakes and my roommate got 15,000 on his Pontiac.