A high-quality automotive battery should last for many years before it needs replacing, and it should be strong enough to properly power all the electrical items in the car during that time. However, it's good to understand how a battery actually operates and how to maintain it, so you don't have it fail sooner than it should. Note a few misconceptions that many people believe when it comes to automotive batteries, so you take care of yours properly and have it last as long as possible.
When a battery is advertised as being maintenance-free, this means that you won't need to occasionally fill it with water, as was needed with older models of automotive batteries. However, having a maintenance-free battery doesn't mean that you never need to inspect that battery or perform any type of work on it; you should still examine any car battery regularly for corrosion around the connectors and for loose cables, and then clean its connectors as well. This will ensure there is no interruption of power to and from the car's battery, so that your vehicle's electrical devices work as they should and so that the battery is always getting recharged as necessary.
Disconnecting the battery
If you're going to have a car sit idle for any length of time, you might assume that you should disconnect the battery, so that it won't get unnecessarily drained of power. However, many electrical devices in the car, including the car's computer, may not respond very well to this extended loss of power, and of needing to be rebooted after the battery is reattached. A better option might be to hook the battery up to a charger when you're ready to use the car again, so that the vehicle is not deprived of power but the battery is also fully charged as needed.
Replacing the battery
Never assume that you can or should replace a car battery yourself, as this is not as simple as you might assume. Batteries come in different sizes so that they fit the car's battery compartment precisely, and even these various sizes will offer different levels of electrical power. Choosing an oversized or underpowered battery can mean one that doesn't fit your vehicle, or one that won't provide all your electrical devices with the power they need. Attaching a new battery to the car's cables improperly can also mean a drained battery and underpowered electronic devices. To avoid these risks, have a mechanic or someone knowledgeable help you choose and install your car's new battery for you.