Question: I want the user to be logged in until the user closes the browser window or specifically logs out. how this can be done? Should I use UserIsOnlineTimeWindow?

Answer: 
Use a javascript "keep alive" mechanism.

You will have to use a javascript setInterval to keep making ajax requests to your server.

This keeps the session alive for as long as the browser is open.

Note that is is a security risk, it is usually good to stop making these requests by clearing the interval after a definitely amount of time.

Extending the session timeout by setting it to very large number won't scale very well for a large number of users
You can set the session timeout in web.config...the max valid value of which 525601 minutes (1 year) - default is 20mins

```
<system.web> 
<sessionState timeout="20" /> 
<system.web> 

```