Will an 80,000 mile auto tire really go 80,000 miles?

When i first bought my brand new car, i installed 80,000 mile tires on it. i figured this would be a good time for a test case for my new car and my new 80,000 mile guraranteed tires. after about 60,000 miles, i drove my tires into the tire shop for an inspection. the tire shop advised me that it was time for a new set of tires. “what happened to my remaining 20,000 miles guaranteed on these set of tires”, i asked? “we will give you credit toward a new set of tires”, he said. question: are there any tires manufactured that will actually go the mileage they promise?