Chris Gerhard wrote a script that determines when one or more users have access to the same SunRay. The person who installs the script can set the hours. When time is up, the work of the person logged on to the SunRay is saved so they can return to their session next time they have access.
Chris describes the script in his blog.
The actual script is saved in his blog resources.
See BigAdmin's scripts section for more scripts like this one.