Check the surfaces that the pins slide on , both the caliper and the mounting bracket, get a flat file and file any nicks, rusted areas smooth, really smooth, and when you reassemble with new pins use a lube (sta lube has one-sylglide or something like that), also check your pads make sure they are wearing evenly, I would also check the spring clip and the anti-rattle clip make sure they are tight-could be the pads are moving around as brakes are applied-new anti rattle clip and some permatex "disc brake quiet" may help there. Check the rotors for warping, and the wheel bearings just to be sure its the pins. .
You should be getting a lot more miles/time than you are. I did my brakes at 65k, 135k. Make sure you replace everything with new parts clips,pins its cheap insurance.
Hope these suggestions help
Steve
91 Navajo 31" w/2 1/2" Rancho Lift & an engine on its way to the machine shop.