I'm expecting the two year old batteries in my 6v bank of 4 to shorten the life of the new pair. I'm hoping to get another 4 years out of these then I'll replace all four. I don't pay too much attention to brand names but I'll buy from suppliers I believe to be reputable. I think they all come from the same two or three manufacturers. FWIW, I just paid $125 each for my 6v batteries.