ASP.NET application is timeout less than 20 minutes. You want to increase the timeout value.
There are several causes for this problem.
1. Change the session state configuration in Web.config (Default: 20 minutes) as listed below in the following script:
<sessionState timeout="120" cookieless="AutoDetect">
2. IIS worker process recycle too often
IIS worker process may recycle less than 20 minutes if you have lots of applications share a same application pool. Usually the problem can be repaired if you put your application in a stand alone application.
3. Change the IIS worker process idle timeout value (Default: 20 minutes)
You can change it by clicking the following: IIS Manager > Application Pools > DefaultAppPool > Properties > Performance.