It depends on a couple of things--do you tow? Do you have a Jake brake? Do you use your brakes often in stop-and-go traffic, etc. I traded a 2000 diesel with 50,000 miles, no Jake brake and I towed a 5th wheel about 20% of the time. Just be fore trading, I took a long trip with the fiver and checked the brakes--they were still plenty good. I had disc/drums--the 4 wheel discs should last longer, I think.
Clayton, that squeaking is probable glazed pads, not bad brakes.