When Trusted Extensions is enabled, users are logged out after 15 minutes of idle time. However, the default value of idletime in the user_attr (1M) database specifies to lock the screen after 30 minutes.
Workaround: To restore the default behavior, add the following properties in the /etc/security/policy.conf file:
idletime=30 idlecmd=lock
Note that the idlecmd setting is ignored unless idletime is also specified. These properties can also be customized for individual users by using the usermod command. For more information, see the usermod (1M) man page.