Just to finish this up, I pulled the rear drums, verified that the rear brakes were in altogether too perfect condition--41K miles, the shoes look like they were installed two months ago. The rear brakes must hardly work, which explains why the front pads haven't lasted. (second set down to the rivets!)
I dicked with the rear adjusters, tightened them up some. They're supposed to self-adjust when the park brake is used...but it's a fookin' automatic transmission, I don't use the park brake. The Leading/Trailing shoe brake design is piss-poor engineering as far as I'm concerned, 'cause I'm not the only person who doesn't stamp the park brake--which means the rear shoes never adjust.
Adding insult to injury, the damned rear drums are less than 9 inches in diameter, with narrow shoes. How powerful could they be? Fookin' GM, cutting corners on the 2nd Gen W-bodies by making disc rear brakes optional when the older cars had decent rear discs as standard equipment.
Anyway, I flushed brake fluid through six bleeder valves--one at each wheel, plus two on the ABS unit. Flushed until I got nice, virgin-clear fluid at each one. One of the ABS bleeder valves sputtered a little before giving me a solid stream of fluid. Pedal height is improved.
Performed my usual after-brake-job test drive to burnish the new pads. Three hard "slows" from 40 mph to 10--15 mph, then several hard "slows" from 70 mph to 40 mph. At that point, the pads seemed nicely bedded; the car didn't shift side-to-side any more when slowing; and the pedal effort for a hard stop reduced considerably. Nice and predictable. I also began to smell the brakes a little. I continued at highway speed for a couple miles, then slowed hard from 90 to 40. Powerful, sure, stable. Good to go!
I don't allow the wheels to "stop" when bedding brake frictions--finned drums and vented rotors are centrifugal air pumps; and I want as much cooling air flow as practical--especially when braking from high speed. Going from 90 to 0, and allowing the brakes to roast with no air flow is brutal--keep the speed up if possible so the air flow carries the heat away. Of course, if traffic conditions require a full stop, that's what you do--but don't hold heavy pressure on the brake pedal while stopped. Release as much pressure as possible while keeping the vehicle stationary. This reduces the heat put into the pads, and therefore the heat put into the calipers and fluid. And the pads/shoes don't "weld" to the rotors/drums. The rotors and drums are designed to get hot; ideally the pads or shoes, calipers, rubber seals, and fluid should be kept cool if practical.