Emails in with already-used subject should append to that topic

On our forum I’ve set the ability to have duplicate topic titles to on because (similar to @Mittineague) we’re going to have a lot of similar topic titles that are potentially completely different in content.

I think it makes sense for those disallowing duplicate topic titles, but perhaps have a setting to limit the length of time this check is carried out for? Default of 3 months say. If a new post comes in and the existing topic is older than that, it gets created as a new topic. Topic title is altered to something else (no idea what to suggest on that front though).