You will definately face this challenge if you are running a multi author WordPress site. You might want to log out inactive user after certain amount of time. For a security conscious site admin, inactive users may pose a session hijacking threat and could easily hack your blog and secure information. That’s why you might have seen in banking and financial sites automatically log out an inactive user automatically. You can add the same functionality in your WordPress multi author site by using WP Idle Logout.
At first get the plugin from above link and upon activation configure the plugin by going to the Settings > Idle Logout menu in your admin menu.
At first you need to setup the Idle time. The default value is 3600 seconds or 1 hour, but you can set it to a lower or higher value as you want. The next option is Idle message. Default message is “You have been logged out due to inactivity”. You can change it to anything you want. And here is the log out notification: