Costco/Kirkland #6 group 25 just showing signs of giving up @ 62 mo. Originally purchase 8/2010. However it has been about 120k+ miles. I concider Kirkland to be a fantastic battery. I get similar performance consistently in each of my 3 vehicles (2 cars, 1larger suv) and. Kirkland battery has been going strong in my Deere 4100 sub-compact tractor. Hopefully will get same from the Interstate. This will be my firstCostco Interstate battery.