I purchased my (2) Kirkland 100 month, group 65 batteries for my 99-F250 diesel and they just now have stared to not hold a charge. I drive in the heat of the desert and the inland heat in San Diego. The truck sits for a couple of months at a time in the winter months since it's more for pulling my boat and camping. I bought the pair at the same time and have never needed to do anything to them. I purchased and installed on 12/04. That's 121 months with no problems! And my original receipt says I paid $59 each. Hope the new Interstates are of the same quality. I have been buying Kirkland Batteries for all my vehicles for over 20 years and will continue to do so at this rate. Thanks Costco! now can you take my MasterCard please? I get better points than on my American express. :-/