Site times out users too quickly, despite web.config specification?

I'm using membership provider and System.Web.Security to manage users. The system logs the user too quickly. I'd like to have the user be able to be idle for at least 1 hour before it times them out (logs them out). I have the following in web.config:

1    <authentication mode="Forms">
2          <forms loginUrl="Login.aspx" timeout="50000"></forms>     
3    </authentication>

I've got a big number, 50000 to ensure a really long idle time "leeway". Maybe this timeout refers to the length of time a session variable "sticks/exists"? Users have only been i ...