It's important not to get into a state of administrative OCD where forums are concerned.
One of the worst things any admin can do in my opinion is to insist that all posts are made in the relevant threads that already exist. After a period of time, it is almost impossible for any subject not to have already been covered, and if a new member opens a thread, then don't moderate it by moving it into a discussion that took place in 1962.
Forums need new 'fresh' threads in order to keep them interesting, and the quickest way to discourage new growth is to tell somebody a subject has already been discussed. It's fine if it has only been discussed recently, but on this forum in particular, we see a lot of threads revisited in order to keep things 'apparantly' tidy, and it can become confusing, and boring. Does it really matter if we start a 'Louis Suarez is a cheat' thread, and 6 months later have a 'Louis Suarez accused of racism thread'?
People enjoy starting threads. Just let them get on with it, and only intervine with sensible and necessary moderating. Anything else is detrimental to the success of any discussion page.
Another thing that really gets on my tits is when peeps open threads with somebody's name, for example 'Joe Bloggs' instead of writing 'Joe Bloggs sent to prison' or 'Happy Birthday Joe Bloggs'. Offering the viewer insight into the content of the thread within the title is more likely to get interest, and also get your forum bigger hits.
As for closing threads, it is unnecessary, unless it is to put a stop to mindless arguments and flaming which have derailed a discussion. Deleting posts and threads is even worse, unless it's spam, as it destroys any history a forum has, and prevents any research, or fact finding, and prevents any comparison to new or old opinion, and so on.
As long as threads are in an appropriate section, leave well alone.