Householdhacker have done a test to determine which battery lasts the longest. Their testing process was fairly simple but effective. They used the exact same brand of flashlight (Maglite Xenon) all straight from the box. Each pair of batteries tested came from different stores around the Portland, OR area. Set 1 came from Fred Meyer, set 2 from Target and set 3 from Safeway. They did this to make sure they used different shipments and manufacturing dates from the battery companies.