WordPress uses AJAX to autosave post revisions to your database as you edit the page/post. WordPress saves a post revision every 60 seconds and you can easily change this time interval. You can change the settings for longer delays in between the autosaves to reduce the amount of post revisions, or decrease the time interval to make sure you never lose change.
Just add following snippet to your wp-config.php file:
define( 'AUTOSAVE_INTERVAL', 160 ); // Seconds
Replace 160 in above code with the your preferred time. Isn’t it easy, right?