I've had the same gel cells for 10 years. I installed them when I got the boat, and havn't looked at them since. Talk about maintainance free. If I leave the boat for the winter, they hardly loose any charge. I have 4, 6-volt batteries for starting and house, and 1, 12 volt for starting the generator. Whatever they cost originally, was worth it to me. I never even think about the batteries.