In addition to be notified when there
is activity on a
thread, you can now be notified when there has been
no activity with the thread.
To activate this, go to the thread that you want to watch, and click the
Watch Settings button near the top of the screen.
The first checkbox is for the normal watch action - notifying you when when there has been a reply to the thread.
The second checkbox is is for the new feature - notifying you when when there has been no activity with the thread for a specified number of day.