That's a good idea. A preface, like...."I know this thread is over a year old, but.....". It's either that or start a new thread on the same topic, and that always brings the classic reply of, "This has already been covered in another thread months ago." It's the forum's own little "catch 22".
Not everyone reads every forum thread every day, so there's always going to be the occasional reviving of an old thread or someone starting a new thread on a subject already covered by an old thread. And there will always be those who reply with something like, "There is already a thread on this subject, use the search option and find it." or, "This thread is three years old.". None of that matters, because what's old to you or me might be new to someone that has never seen it.
So maybe every thread should start with an apologetic comment like, "I apologize if this has already been covered in an older thread." Or, "Sorry to revive this old thread, but I just found it in the archives." This would keep everyone on the same page.