One of the problems is an announcement is no longer an announcement after a month to say the least. They should be moved into a "on-going" sub-forum instead of staying in the Announcments sub-forum. All it takes is an "interested" post to put an old announement thread back on top, causing clutter.
I suggest the admin put a time limit on announcements, if possible.
Great idea, the only thing is that I think they will adept to this by creating new very small announcements constantly