The front caliper brake pads and rotor are easy to see and monitor with expected wear intervals. The rear drum brakes are not so easy to see on a monthly basis. A few years ago I hammered the drums apart during a tire rotation. After looking at them and a picture of what a new one would look there wasn't the dramatic difference I was expecting. Doing a big guess of how much it wore down since new and how much father it could go it seems like they could go to 500,000, which seems high to me for any wear item. I was thinking of replacing them just because 27 years and 300,000 seems like I should do something. So, can rear drum brakes actually make it to 30 years 400,000 or should I have a shop do the $50 inspection.