This might not be the exact/precise answer to yer ponder ma'am but this is just my foresight on the matter.
I do not perceive a thread to have been necro-threaded unless that thread is solidly over 2-3 months of inactivity. Might be a bit lineal on this though. Also, I do know that any off-topic threads (other games, forum games, off-topic discussion, etc) actually can very rarely be considered necro-threaded due to it's quite a'ight to post in these topics any time ye' wish. No matter if they may be a year or two old since they will not add to yer post count. The same goes with the FeralHeart add-ons and any thread that's a current work in progress. We wish not to lock a thread that the creator of said thread can easily return to and add onto what they've posted thus far instead of havin' to make a whole other thread coverin' the same topic. That will only add clutter to the boards.
My apologies for the somewhat vague response for even I am still gettin' the gist of all this myself.