On my Chevy Colorado, oem rear brakes (New), only have about 5 mm of rear brake pad (drum brakes), at 33,000 miles during a brake inspection was told they were worn. I didnt know how thin New pad material was on these brakes and evidently neither did the repair shop. So I let them replace the pads (with some generic pads they obtained), also had them flush the ainti lock brake system. Upon driving the vehicle away, the brakes felt weak, and I took the vehicle back, and they reflush and bled. It was alittle better, but not as good as the supposedly worn brakes , that was on the vehicle when I took it in. The mechanic said, he works so many vehicles that he doesn't know what normal is. Anyway done deal, 40,000 miles later I think rear brakes should be coming due, and take it to a different repair shop.
They said on this type of brake (no rivets), you want to wear them all the way down, plenty of life, ended up changing them any way(rayovac), cause they only looked to have a few mm, not knowing (new pads are only about 5 mm).
40,000 mile later, I go to another dealer, to have my front brakes checked, they said front pads are fine , but your rear pads are worn and drums out of spec. Plus axle seals leaking. 4 or 500 dollar estimate. So I went up to see. So I see the pads and they look okay to me (and the actual tech said so)(different from what the manager said), but I took their word on the drums, cause I knew they'd been turned twice. But the axle seals weren't leaking, ,maybe a tinge of dampness around the seal, so I thought fixing all this, is a waste of money, looks fine to me. Paid the rack charge and on my way.
Later I went on and bought new drums, when I measured, they were no different than the ones I pulled off so I took them back and got my money back.
20,000 miles later, I decided to do my own rear brake pads ( bought Bendix) oem quality manufacture. It was tough, the brake cable needs a special compress tool , plus had to modify that tool. Once together OMG, brakes were the strongest they've ever been since NEW, after messing with different shops, installing generic stuff. Still running those same drums.