There may be a few other things that factor into this as well. I try to keep my vehicles relatively clean, inside and out, underneath to, engine compartment.........So when I wash my vehicles occasionally I lean down under the front bumper and wash the insides of the wheels off as well, concentrate the pressure on the caliper area to. You would be surprised at how much gunk can build up in these areas! Wash the back brakes off from the inside out as well. If you have recently been through a mud bog I would pay close attention to how much stuff was packed up under the vehicle and where.
If you are going to perform the brake job yourself then educate yourself on a few key areas you need to be aware of; Look at the pads, you are looking for even wear from side to side (inboard pad vs outboard pad), You want the pad to be close to the same thickness all across it. None of this requires the use of calipers either, you can usually see the differences if the pads have not been wearing evenly. If an inboard pad is half the thickness of the outer, on the same caliper, then you probably have a problem somewhere, like a sticking caliper or something.
One more thing, the mechanics use to tell everyone to set their E-Brake on a monthly basis, or more often, when parking the vehicle. They discovered that not using those systems could cause all sorts of problems with the rear brakes. Me and the wife always set our E-Brakes on all of our vehicles, no matter where we park, that way we know if you get into one it is set!