The average lifespan of a car battery under normal conditions is four years. Normal circumstances require full charge cycles and limited exposure to any extreme temperatures. Additional devices such as MP3 players and GPS also deplete the life of a battery.
Begin scheduling battery tests after two years of use and then once a year after that. Car batteries are often exposed to extreme heat, and they do not run at optimal conditions after years of use in hot climates. Heat damages batteries, and they fail to start during the winter because the battery solution is weakened due to heat exposure.