Where can I change the length of time before the inactivity
triggers a log out? I'm not seeing it in the preferences, but
maybe I'm just looking in the wrong place.
The setting is in the "System > Defaults" menu; "Session Timeout" (3rd item in the "Security settings" section). The default is the litteral text "90 minutes". If you want it to time out after 3 hours, make that "180 minutes" or "3 hours".
HTH,