Personally I prefer newer threads with links to old threads. That is how we can have fresher threads with connections to other threads of same subjects Especially if threads become too long ( 3 or more pages each)
Having said that, I prefer leaving the whole thing to the market or nature or whatever, with NO control of any sort.
If some folks are ineterested in a subject, they keep it up and alive. If no one is interested in the thread, it will sink to the bottom on its own.
just my 2 cents