I may seem like a slacker in all this, but I did nothing with my Meritor brakes for 250,000 miles except as follows.
The pads wore unevenly with one (inner or outer getting the wear but I cannot remember which) so I initially replaced both.
From that point on I was very careful to insure the pins were not bound up by moving them slightly at each of my 5000 mile service intervals. I gave the rotating slack adjuster shaft only a single shot of grease. By that I mean using my drum of grease with its dedicated grease pump, I pulled the trigger on the grease gun, heard one pump, and stopped. There were two fittings and each got one shot.
To verify the slack adjuster setting was OK I annually had the slack adjuster travel checked (wife stepped on the brakes, I was under the coach and measured) to verify the travel was within the specified range. I think I was allowed something around an inch on tag and steers and I never saw the red ring around the brake chamber push rod. It might have been 5/8″ but I just cannot remember.
Except for pad replacement and insuring free pins and correct slack adjuster motion, I did nothing. Call me lazy or whatever, but I never had an issue.