As an end user I want the ThinLinc Client to disconnect from a server when it has been idle for a given amount of time so that I can be sure that no-one else can use my ThinLinc Session if I forget a session running on a computer. This is slightly different from the current server-side -IdleTimeout setting to Xvnc. The current idle timeout mechanism is focused on what the system administrator deems necessary, while this would be targeted to letting the end user decide for themselves.
See also bug 5179.