When I check in Activity Monitor of SQL Server 2005 I also see few connections in sleeping status. I understand if C#.NET application is using Pooling, for performance reason SQL Server does not destroy those connections for LIMITED TIME even if you have closed that connection. But what If C#.NET application is using pooling and closing connections after finishing with it but even after 6-7 days those connections are still in sleeping mode. I can tell this by Last Batch column from Activity Monitor.

FYI once my application starts we don’t close that application until we have to restart our machine due to Windows updates, means our application runs for long period of time without restart.

In the attached screenshot you can see that some connections were created at 27/08/2008 and their last batch was same time but even after 8 days they are still sleeping. Shouldn't they destroyed by SQL Server??