My original Monte I purchased in 1970, the front pads lasted nearly 50,000 miles. 40,000 or more of that was open highway miles. When they needed replaced I put semi metalic pads on and they overheated and wore out due to the overheating and warped my rotors after 1500 miles. Not knowing any better, I put another set and new rotors on with the same results. Next I had a garage do the work for me but I purchased the parts, again semi metalic. They rebuilt the calipers, and replaced the perportioning valve, 1500 miles later they were bad again due to overheating. When I finally took it to Chevrolet, they told me the pads must be Organic pads not semi metalic or performance. The entire problem was the semi metalic pads are too hard and I think the performance pads are even harder. The organic pads are softer and do the job properly.
I hope this helps
Rob