I agree with those that recommended to stay with your GC batteries. My 2 6v Sam's Club GC batteries are 14 years old now and have served me well. Every year I expect to have to buy a new set and I equalize and desulfate them and they still get me through a week of dry camping with out generator usage(I only dry Camp). I think maintenance is key to how long they will last. Try to equalize and desufate to see if you can restore capacity. If not the only thing I would check before buying from Sam's or Costco is to see what GC batteries they now carry. Sam's and Costco change their suppliers from time to time and some on here report the newer Costco batteries are not lasting as long.