How long the battery lasts depends on which kind you got. The average lifespan of such a battery is two years.
They provide a lot of information on how to maintain your battery. Yuasa Battery also will help you perform this maintenance and answer any questions you might have.
You can use, for example, a Yuasa YTZ14S motorcycle battery.
YTZ12S from Yuasa
It depends on how often you are using and recharging the battery. An average life span for a remote control plane battery is 6 months to 1 year long.
That depends on what you are doing.
Automotive Batteries.
Yasuo Yuasa has written: 'Kodaijin no seishin sekai' -- subject(s): Japan, Intellectual life
Properly store and maintain your Yuasa batteries for maximum life expectancy. Disconnect the battery cables of an infrequently used vehicle, and charge it every two weeks. Remove the battery from the vehicle. Charge it fully, and store safely away from children. In climates above 60 degrees, recharge the battery every two weeks, and for cooler climates, once per month.
If the battery is not a deep cycle battery, allowing the battery to run down dead multiple times will shorten its life span.
Leaving something on (like headlights) for an extended amount of time without the engine running will shorten the life span of the battery unless the battery is the deep cycle type. Overcharging an automotive battery will also shorten its life span.
You can use, for example, a Yuasa MF YTX16-BS or an equal size battery.
Yuasa batteries are available at amazon.com and receive very high ratings. Additionally, the prices on amazon seem comparable to pricing at other sites.