22,000 miles seems a little early, but brake life depends very much on the driver, payload, and type of usage. I had one freind who was a left foot braker. He drove with his left foot perched over the brake pedal. If you followed him he would drive you crazy becasue he was constantly flashing the brake lights because he was constantly just tapping the brakes when he hit small bumps. He could wear out a set of brake pads in 20,000 miles. I usually get at least 60k on a set of pads, but then I try to avoid using the brakes as much as possible. My sister routinely has pads last more than 80K miles (I think the front pads on her Civic made it to 97k miles).
If you are carrying a lot of heavy loads, and/or do a lot of stop and go driving, and/or do a lot of high performance driving, you can expect shorter pad life. If you want longer pad life, anticiapte stops and slow down without the brakes as you approach them. Try to avoid a lot of full tilt stops. I suspect you are a high performance driver who likes to brake firmly when coming to an intersection. If you are driving around empty, the front brakes are probably doing almost all the work when you stop firmly. With your old Discovery, the rear brakes probably provided a larger percentage of the force needed to stop the truck (becasue there was a larger percentage of the total weight on the rear axle), and therefore you spread the wear over the front and rear brakes better than with a lightly loaded pick-up.
Ed