Andy,
Threads are often left open and unanswered. Sometimes nobody knows the answer. In very active forums, threads disappear quickly so they are not seen. If someone wants an answer, a thread can be "bumped" up to the top with a new post to the thread. Or as most people do, a new thread can be created.
I suspect that few people post back if they find an answer on their own or from another source. I appreciate it when someone posts a message indicating the issue has been resolved but it doesn't happen often. There are no rules that say you have to do that. Like many newsgroups, there is no "cleanup" done.
Personally, I usually ignore messages that are more than a week old. In the most active forums, I may never see messages older than two or three days. Therefore, I would not have bothered to post a reply to the 1st message in this thread at this late date. Terry L. Broadbent
FAQ183-874 contains tips for posting questions in these forums.
NOTE: Reference to the FAQ is not directed at any individual.