The problem there is that it would very difficult to make a fair distinction between the two. A type 1 discussion that is still forging ahead after a month vs a type 2 that's on its third lap around the same small track are both still active threads, and which would require a Moderator to actively monitor them to see the shape of the track.
Originally Posted by Frog march
I would suggest that there be a provision for a thread to be reopened based on PM's to the moderators from the members actually in the discussion. Maybe even preemptively. Have the moderator watching the clock post a 1 week warning or something. Then, see how many people who are not the person that proposed the idea PM a request to extend it for one additional month. Compare them to the post count in the thread to be sure that the PM's came from active thread participants, then post the decision about whether or not it will be extended with the default being "no".
I'm Not Evil.
An evil person would do the things that pop into my head.