2 months is way too short to justify closing a forum post. I have recently hit a few unresolved topics that closed this month on which I wanted to join the discussion (some of which met no resolution). Now, I will be forced to completely re-introduce the same topic in the form of a new forum post that lacks the useful context of the post that closed too soon.
This may just be my opinion, but I think it will reduce duplicate topics. If the moderators need an old post closed, they can lock it... as for unresolved posts, though, those could use a longer life. I think this will benefit the community.