Since Android is a rapidly evolving platform, it is important to maintain current software for Android Studio and plugin updates, and for the Android SDK (both Platforms and Tools). The AS platform will probably notify automatically of possible updates, but you can also check for them yourself:
On a related note, it is also good practice to keep abreast of the latest online Android documentation, since best practices evolve and some classes and methods in previously-written apps may be deprecated in favor of newer ones over time. Because of backward compatibility your app will likely still work, but there may be advantages to updating older apps to take advantage of newer capabilities of the SDK.
Last modified: June 9, 2016