Don't know how it is in the rest of the country, but this is what my family learned in many years of having an auto parts store in Houston, Texas. Any battery, no matter how many CCA, is suspect after 3 years of service. The heat and humidity down here will take them down! Also the first time it gets really cold/damp after a while of warm, or vice versa, marginal batteries or starting/charging systems will make themselves known. And one bad part or connection will domino if left unfixed. That said, l know it's not always feasible to fix something right away, especially if you're DD'ing the vehicle or working outside. Thankfully the GMT400 series is usually more forgiving of their owners ' lapses....