Not always.
The Google store usually updates quickly, within 24 hours of a release.
The Amazon store does lag, generally by multiple versions, due to Amazon policies. In this case, side loading may be desirable.
As you mention, sideloading forces you to a manual update process. To return to automatic updates, delete the sideloaded version and re-install from the appropriate app store.
Subscribe to the announcement thread to be notified of new releases. Scroll to the bottom of the thread and change Normal to Watching.
