Set interval and the number of previous posts number autosave

Edit wp-config.php file to set time for autosaving posts, pages,.. and the number of post or pages previous versions – revisions.

define('AUTOSAVE_INTERVAL', 120 );  // Autosave every 2 minutes 

define('WP_POST_REVISIONS', 3); // 3 previuos versions would be 
                                //available to take a look and restore