If the thread is buried numerous pages back (with the exception of forum games), it would be considered Necroe'd. Especially if the necro is spam. However, if the post reignites the conversation, then it won't be as likely to be locked as a necro.
The only thing to add to this is that time is relative. It's a safe bet that posting year-old threads will be necroing, but posting in, say, one-month old threads will not be. If you're really wanting to post in a thread that's that old, it's just better to recreate a thread. It's okay to make a duplicate thread if the original is really old. We ain't the time police (though that would be sweet).
As the thread gets older, the likelihood of us wanting you to make a newer thread increases.
To everyone else: Pay attention to what time the "most recent post" in the forum says.
but posting in, say, one-month old threads will not be
Unless you are a complete moron, spam, and no one is there to get the thread up and running properly.
To be completely honest, a thread is too old when a mod deems it to be. You won't get told of (by us) for posting in a two months old thread by accident once in a while, but if you accidentally post in a two year old thread, we will probably mention you should check the times in the thread, and if you systematically go two years back and post in thread, we are most likely going to be pissed at you.
another good thing to do, is to check through the first 10-15 pages or so before posting a new topic, to see if its been answered, or already exists, so it is not locked as [dup] duplicate
