ASP.NET 4.0 How to make session values alive still user logout.

Hi guys,
 

I am getting a problem one of my web site. My site having login screen, user should login to do operations. so this site automatically time out on 20 min. because ISS ideal time default 20 min as i read in one of the article, and i got solution to make it '0' to never expire, but still my session expire on 20 min.
 
And another solution i have to make session state =60/what ever time i required but this is also not helping, me.

 

So please guide me the solution
 
How to make session values alive still user logout.
 
Thanks and regards
 
Vishwa