Batteries "are like a box of chocolates, you never know what you are going to get". What the manufacturer sells you is that you will have "a battery" not necessarily "the battery" for the length of the Full Replacement Warranty period which on the average is limited to no more than two years. Anything after that you could be having a battery on a prorated basis. Is it good luck that your battery outlived its warranty? You tell me. We usually tend to look at battery life and its performance in automobile terms but in a boat battery performance becomes more critical. That performance and reliability aspects that we seek outweigh battery life considerations. There are clear indications that when using the proper equipment and following proper charging and maintenance guidelines that we can extend battery life but even then there are no guarantees. Some batteries you simply cannot kill while others will come to an early death irrespective. I happen to like the least expensive wet cell batteries on the market that come with a fair warranty and the reason I like them is, 1) their chances of a long useful life are similar to any other battery 2) If I ever need a replacement battery in an emergency it is just a question of going ashore and finding a Walmart or an auto parts retailer. Trying to find matching fancy Gel batteries when in the boondocks could be trying. Just some food for thought.