I personally think that there is a good justification for a number of other reasons to close certain categories of thread. Many BS threads are topical and "personal" in the nicer sense, Happy Birthday threads and the like. Once the event has passed - a couple of weeks beyond, they serve no further purpose, why not close them for further posts. It may be interesting to read some old threads the following year, but not good reason to add postings.

There are a lot of threads which advertise a specific dated event. These are a kind of thread different from the blatant self-advertisement threads (no objection to those either) which keep a particular performers in out collective consciousness. Event based threads have a short shelf life. Once the event has happened, where do they belong? (There is currently one advertising the Yorkshire Mudcat Gathering - its main purpose is to inform about when and where - its secondary purpose is for attendees to comment imediately after the event - once that time has passed, new postings do not really serve much purpose, if any. If you want to discuss the event at a later date doesn't the discussion deserve a thread of its own? Keep the original for reference, but close it to new postings - you can always put a BLICKY to the original if you want people to read it.

Just a couple of thoughts!
Quack!
Geoff the Duck.