Old thread warning recommendation

I saw this on another forum. Might be worth adding to old threads when a member attempts to post;

Old Thread Warning!

This thread is more than 105 days old. It is very likely that it does not need any further discussion and replying to it will serve no purpose. However, if you feel it is necessary to make a new reply, you can still do so.
<input type="checkbox" class="acceptPostAge" defaultchecked="false" style="margin: 1px 0px 0px; padding: 0px; float: left;">I am aware that this thread is old, but I still want to post a reply.

Yeah that's not a bad idea. Although wouldn't stop the spam-necro'ers who are just doing it to get their post count up.

On some boards I've seen posts be automatically locked after 6/12 months without anyone posting in it - that's another option perhaps? A 12 month old thread probably has out of date info in it anyway (especially in this industry).