The batteries at Costco these days are Interstate brand specifically made for Costco and carry a great warranty.....easy at Costco, no hassles if there's a problem and are around $80 each.

I get 4 years out of my batteries (have 2) but I always have them on a desulfation charger/maintainer and they easily last 4 years......I just replace one every 2 years just to keep them fresh........$40 a year for batteries is cheap insurance to always make sure you're ready to go on the water.......life's too short for a dead battery