The experience on Fire TV requires you to think about designing for the 10-foot experience as well as taking into account different control interfaces, like a remote and voice capabilities.
Fire OS-based devices update apps automatically and, as a developer, you can expect that most of your users will transition to the latest version of your app in a matter of days. Some users, however, turn this functionality off. On some devices, like phones, this often gets turned off to save data.