I have four wheel disc brakes on my 4x4 (135K mi). I have read posts about the "horsecollar" shoe arrangement on the rear disc/drum arrangement. I have serviced (replace disc/drum and shoe yoke) these once before myself and know how to get the disc/drum off with a little effort (heat, puller, hammer, pb rust). I take apart the little piston/plunger thingy, clean it, grease it, tension up and put everything back together. I think the system sucks. I don't know why it is not self adjusting.
Is there an aftermarket product out there that works better/holds better? With a boat on a ramp this arrangement is not the best thing in the world. The parking brake generally degrades after a few months of use after service. I can't see having to take it apart every year for adjustment. I have a three year old Hyundai Elantra (135K mi) with rear drums and I have not serviced them yet. The parking brake holds like a charm.
I also have the same problem with my ebrake on my silverado, I seem to adjust it every summer and it works mildly well for a month or so but then loses all grip. I hope to be replacing the entire rotor/pads/e pads soon and be able to see if that helps.