The xbAutoSave plugin v2.0 allows content (articles) being edited in the backend (Administrator site) to be automatically saved if changes have been made. The interval at which the save occurs is a configurable option. In addition it also allows for the use of keystrokes Ctrl+S and Cmd+S (Mac) to be used to save. Timed save and keystroke save can be enabled separately.

There are a couple of points to note:

The plugin is automatically disabled when creating a new article until it has been saved manually (using the standard Joomla [Save] button). This is because you want to be sure that you have set the basic options for a new article - published status, category, access permissions, publishing options and so on - before Autosave kicks in and goes and saves your incomplete work as a new published article visible to all with no category (the Joomla defaults if you don't change them).

If you are using the Joomla versioning system then you need to be aware that everytime an autosave or keystroke save occurs a new version is added. If your autosave interval is short you will rapidly overwrite the limited number (default 10) of versions that Joomla tracks with potentially trivial updates.

It is good practice therefore when you open an article for editing to consider marking the last saved version to 'Keep'. 

The plugin reminds you of both of these items with a message when you start an editing session on an article.

The Option settings are very straightforward. You can enable either Timed saving or Keystroke saving or both, and set the interval in seconds for timed saves. The minimum time is 30 secs as less than that tends to cause problems. Generally you will want to set it less than your session timeout (which is set in minutes under | Global Configuration | System | tab.) Personally I find about 60 seconds useful as that is how long it takes me to realise that I have deleted something in error :-)