Open ended question on how long the batteries should last. Depends on many things as to how much are they used, are they maintained properly, charged properly....etc. I have always heard the rule of thumb was 2 years on boat deep cycle batteries. I am not a weekend warrior on the water but do/did get a chance to fish I guess average amount of time and I get 3 years to 4 years out of mine. I use Carquest Gold Deep Cycle Marine batteries and LOVE them. They never run out of charge and I don't lose any thrust even during some 16 hour days on the water and this is pulling my 17 foot Deep V aluminum boat, my big behind, a buddy and probably 100lbs of fishing tackle that I take with me plus all the other typical boat accessories. This topic has been discussed many times just as line type so you will probably get many different opinions on the topic. Some guys like using Walmart Batteries because of the easy replacement and access to Walmarts if they go bad. I am on my second set of the Carquest and the first set worked so well that I made sure I bought the same the second time. I am getting the same results and see no difference, so I would bet they are all good.