Cooper is about normal, seems like people get about 40,000 miles out of them. I think they are a decent budget tire but i feel they are not in the same ballpark as Toyo and General and Continental lines for quality and durability. How many times have you had to rebalance those coopers? Typically most owners are seeing the shake in the steering wheel and seats and need to rebalance about every 15,000-20,000 miles. This is due to the cords in the tire changing their direction and splaying backwards as the tire rotates forwards. Honestly the newer BFG AT are one of the worst, seems like everyone is having to rebalance them at 10,000-15,000 and most folks on heavier trucks are wearing them out in 35,000 miles or so.
The Toyo AT appear to last about 60,000 on most light trucks like ours and rebalances are about every 20,000-30,000 or so, they are expensive but they are higher quality than walmart brand and other bargain brands. Me personally i prefer the General AT line, the current is the AT/X and it is by far my favorite tire. Amazing in pretty much everything you put in front of it, it goes anywhere and everywhere you can think, snow, ice, sleet, rain, it doesnt hydroplane, it steers well, its quiet, and it lasts.
My 4runner has 98,000 miles on a set of General AT/X LRE tires, and even though they are load range E meaning 10 ply, they ride smooth and soft, far better than you can imagine. I run 25-26psi in the front and 22 in the rear and they lay out perfectly flat on the road and the ride is soft and the mileage is unbeatable. They are 6 years old now, and starting to fall apart, the tread is getting hard and cracking and the lugs are chunking off from the gravel roads i drive. The tread however still has another 25,000 miles of life left on them. I bet i could get to 130,000 if the tire wouldnt fall apart.
Oh, i rebalanced and rotated them for their first time at 40,000 miles. I just rebalanced and rotated them for their second time at 90,000 miles. I have owned a half dozen sets of these tires and they are getting 60,000 on my dually that pulls a trailer every day of its life, and about 70,000 on my 2500 SRW diesel that doubles as a daily driver and pull toy. These are my favorite tire but i doubt they are on the buy three get one free deals.