Most drivers operate on the assumption that a car battery should last as long as the vehicle. That assumption causes most avoidable roadside calls. The realistic expected lifespan of a flooded lead-acid battery is three to five years in moderate climates.
Climate matters enormously. Cold-weather climates extend life slightly (four to six years) because cold slows the discharge cycle. Hot climates shorten it (two-and-a-half to four years) because heat accelerates plate degradation. Phoenix and Las Vegas consistently see the shortest battery lives in the country.
AGM batteries last slightly longer but cost two to three times more. If your vehicle has start-stop or is a luxury/performance car, AGM is required — replacing with a cheaper flooded battery will fail prematurely.
Driving pattern matters more than most realize. Short trips don't allow the alternator to fully recharge. Over months, the battery operates undercharged, sulfation accelerates. A weekly longer drive or an overnight smart maintainer can extend life by 30–50%.
Warning signs before failure: slow cranking in the morning, dimming headlights at idle, accessories blinking during start, corrosion on terminals, dashboard battery warning light.