This is such an essential add-on, to get users to 'notice' before they reply to just any thread. I re-worded our notice to read:
This thread is more than x years old.
So, previous particpants may no longer be on the board at this time. If it dealt with 'current' events, it no longer requires further comment.
If not though, FEEL FREE to reply and bring the thread back into active discussion.
To date, we have not had a single-thread brought back into live discussion by accident. This just works!