Explanation/Reference:
With a timeout, overload mode is set if the time elapsed since the IS-IS instance started is less than the specified timeout.
To specify the number of seconds at which overload is reset, include the timeout option when specifying the overload statement:
overload timeout seconds;
The time can range from 60 through 1800 seconds.
References: http://www.juniper.net/documentation/en_US/junos12.1x47/topics/usage-guidelines/routing- configuring-is-is-to-make-routers-appear-overloaded.html