How often to replace a battery .

5 years is about the life span of a good battery. But it depends on your driving habits, a history of short trips-- start, go to store, off, start, home. It has X-Number of start/charge cycles among other factors. But look at the cable connections, if there is corrosion, looks sorta like mold growing, baking soda and water will clean those and if they must come off to clean use a wire brush or better one of these, can be bought at Dollar store Then vaseline on the terminals will prevent it from happening again

If you do buy a battery, invest in a good one. A $150 Interstate may sound expensive..well it is I guess..but a $50 battery will strand you at the worst possible time