Yes I've hit the same problem, we are small company with 70 users, that's 14k to logout idle users.
I'm now looking at a combination of the script mohdaoud.blogspot.com/.../script-to-get-users-logged-in-to-gp_2325.html and checking for locked objects to determine if its "safe" to logout none admin users after an hour of inactivity via a SQL server job.