However, i would appreciate if you read thru ..to get the exact understanding of how & when it would work.
Firstly, you need to increase the timeout of the executionTimeout attribute of the httpRuntime element. Note that this is mentioned in Seconds unlike the other timeout attributes like the Session timeout and others.
And moreover, this attribute takes effect only when you set the debug attribute of the Compilation element to false. This is also specified in the MSDN link that you mentioned. Like,
But this works in conjunction with the Session timeout. Yes, if the session times out , then an error would be thrown. and it wouldn't wait for the executionTimeout value to take effect. so you also need to set the Session Timeout to a higher value. And note that this is in minutes. which would look like,
And note that all of this would be overriden by AppPool recycling process. so you need to set the Idle Timeout value of the Apppool that your website uses to atleast same / higher value than the session timeout.