Who Makes the Longest Lasting Deep Cycle Battery? By longest lasting, I mean both in keeping a large charge capacity and durability/life span. Other than Spoonbilling, 80% of the time my boat sees the water it is dark or close to it, so we need 2 large deep cycle batteries for all our lights and electronics. We currently have 2 of the large AC Delco deep cycles (plus our cranking battery), which we have been very happy with. But the 2 are entering their 5th year of service and are needing replaced. Is 5 years about normal for the life of a deep cycle? I have been very pleased with the performance of the AC Delco, but was wondering what everyone else thought or what they were using. Since we spend out so much time at night, we don't mind getting the top of the line as the life of the batteries can make or break a trip. What do you all think?