I posted another quick little workflow on my vCO blog, this is one that you can schedule to run daily and it will disconnect old idle sessions.
It includes a white list of accounts that you never want to disconnect and you can configure the number of minutes that the session has to have been idle for before it gets terminated.
http://ullberg.us/orchestrate/122/clean-up-idle-sessions
As always, feedback is very much appreciated (either here or on the blog).