WordPress developers add AutoSave feature into the popular blog publishing system since the release of WordPress 2.1, and it has became the permanent fixture in all future generation of WordPress, including WordPress 2.5 and WordPress 2.6 branches. By default, WordPress AutoSave will automatically save and store the unsaved and in-editing draft or published post/page every 60 seconds.
To change the frequency or the duration interval of which WordPress will auto-save the data and content in the HTML or Visual Editor, use the AUTOSAVE_INTERVAL constant to configure and set a new value for the interval duration. The constant can be added in the wp-config.php WordPress configuration file, which located in the root directory of the blog.
The syntax to be added to the wp-config.php to modify or change the AutoSave interval in WordPress:
Code in line above will instruct WordPress to auto-save a post or page every 300 seconds (or 5 minutes). If you want to specify a different time interval between auto-saved copy, just change the time value accordingly (in seconds).