How long a car battery lasts depends on many variables including your driving habits, the climate you live in, and how well your car runs. This typically can range from one to seven years, with the average being around four or five. A good rule of thumb would be to automatically have your battery changed within that four to five year range, or to look for signs such as dimming headlights that indicate that your battery is dying. A car battery should be changed every 5 years as long as no problems in power supply occur.