With proper maintenance, the average life expectancy of car batteries is about 55 months.

LEAD-ACID BATTERY CHARGING:
Battery low on power? You might not need a replacement just yet. These recommended charging procedures can help you keep your battery operating at full power.
Before charging your battery, refer to your owner’s manual and your battery charger manual for instructions. Review the safety instructions that came with your charger and battery. Remember that batteries contain sulfuric acid that can cause severe burns, and hydrogen-oxygen gases that can be explosive.

Observe the following guidelines when charging:
# Make sure the battery terminals are clean and free from corrosion.
# Do not attempt to charge a dried-out battery. If needed, add distilled (or drinking) water to just above the battery plates. Do not overfill.
# Refer to any written instructions provided by the battery and charger manufacturers.
# Identify the positive and negative terminals of the battery and attach the correct charger leads.
# If charging a battery connected to a vehicle, be sure that the vehicle’s electrical system has protection against overvoltage or be sure that the charger will not have high-charging voltages that may damage the vehicle’s electrical system.

MAINTENANCE:
STORAGE TIPS
The most important consideration when storing any battery is to make sure the voltage never drops below 12.4 volts. Following these simple tips on battery maintenance can help extend the life of your battery.
If you are storing the battery for an extended period of time, one of the best ways to prevent damage is to make sure the voltage never drops below 12.4 volts. We recommend using a type of "battery maintainer" – a device that will monitor your battery and keep it at full potential during storage. There are two types of maintenance chargers:
Traditional "float" chargers, which provide constant voltage with tapering amperage to the battery even when it is fully charged. The typical floating charging voltage ranges from 13.0 to 13.8 volts.
Fully automatic multistage or multistep chargers, which monitor the battery and charge it as necessary. Multistage maintainers will charge at varying voltages and varying amperage. Some of these multistep chargers are also capable of working well as a battery charger.
If it is not possible to use a maintenance charger, disconnect the battery from the vehicle during storage to prevent the vehicle from discharging the battery. Always provide a full charge with a battery charger prior to storage, then check the battery voltage every three to six months and charge if it falls below 12.4 volts. Also, when possible, store your battery in a cool, dry location.

OTHER MAINTENANCE TIPS
# Check your battery every now and then to make sure its terminal connections are clean, snug and protected from the elements. Signs of corrosion or leakage could mean that your battery is no longer operating as well as it should.
# Always unplug accessories and turn off lights when your car is turned off.
# Keep the battery in cooler places whenever possible. Heat damages batteries.
# Scrub corrosion from the terminals with a solution of water and baking soda.

Source : http://www.autobatteries.com/en-us/battery-care/maintenance-charging/