To my way of thinking, it is not "how old" the topic may be that is the real question, but whether or not they have something worthwhile and substantive to offer to the topic in resurrecting it.
It would be my assertion that, if the person posting has nothing of substance to offer to the topic, and the last post was more than a year ago, then they should not be permitted to post in it (and a moderator should handle it...reported or no).
The question becomes what defines "substance"? Word English Dictionary (from the dictionary.com website) defines "substance", as it relates here, as:
the essence, meaning, etc, of a written or spoken thought;
solid or meaningful quality
The usual answers given on topics by members, such as (and these are some real quotes from topics in the Balto forums):
"I agree with Kodi!

"
"Good point on both of those."
"I have the Balto soundtrack!!!!!!!"
"i think so too."
"She was cool. I didn't mind her."
And that's just a tiny sampling of the kinds of inept, vacuous and pointless postings people often throw into topics...dead or otherwise, which cause so much consternation (and the reason why that rule came into existence). And these types of posts are almost ALWAYS what appear as new ones in otherwise long-dead (or even not-so-long dead) topics.
It seems a rather frustrating pattern for some of us that there are newbies AND noobs out there who consistently seek out OLD topics to do their first forum posts in, rather than the newer topics which occupy the top half of the first page of any particular board in the forum. And they do it on several boards, and some do it repeatedly and consistently, regardless of being advised that they really ought not to, and that there are plenty of newer topics (and sometimes newer topics with the same subject) to post in.
Um, however, it is worth noting that the rule about posting in old topics was changed sometime during the course of 2012 or very early 2013...WITHOUT anyone being advised of it. To wit (from the site rules page):
10. Starting a topic - When you start a new topic, make sure you start it in the right section. Bringing back old topics IS allowed
(even topics from years ago). Making new topics even though there's already one similar is allowed,
except if the previous topic appears on the same page.