Thank you Gabe, for taking a part into this discussion. You are right that "The way ASP.NET handles authentication it will do a redirect back to where you were before hitting submit".
The viewstate for the editor is enabled but when your session timeouts, the viewstate information is destroyed. The only possible solution is this information to be saved somehow when the session timeouts and restored on logon.
We will consider such feature in some of our next releases.
What you can do to avoid this is increase the time of inactivity after which Sitefinity will force you to log in. This can be tuned in the web.config
| <forms name=".ASPNET"
| path="/" />
The value is in seconds.
the Telerik team