Timed Out Problem in ASP.NET Application

We are using Windows authentication for our ASP.NET application deployed to a SharePoint environment. All the web pages in our application are timing out beyond 20 minutes of idle time and the users are not able to update records beyond that. We do not want the pages to time out or at least increase it to 60 minutes. Any help/tip to resolve this would be greatly appreciated.

Note: We have tried out setting session state timeout (IIS, Web.config), didn’t work