Susan's point about "locking" threads is a good one; I'm fairly sure I've seen it done here in the past. It would also be helpful, where a thread has become very long and a sequel started, to prevent people from posting any more to the old part; in spite of clear requests to the contrary, a good many folk (some mere idiots, but many who really should know better) regularly do this, often to repeat information already given earlier on in a discussion which -because it was already over-long- they have not bothered to read...