I've had the same rig for many years with a four 6V battery bank. First batteries lasted 8 years, changed the second batteries after 6 years and the newest are still fine. I have never even heard of someone losing a cell in good quality (or other wise) flooded 6 volt battery. Its just not something to normally make decisions on. Don't forget to check fluid levels, especially when being plugged into 120 volts, which I assume you are, if not hooked into solar power. Try to keep ussage to 50% or above, with 6V. deep cycle golf-cart style batteries. All my batteries were bought in the south. As the 6-Volt battery has only three cells, are the chances of cell failure less?