Do you have the archive enabled on your forum? Most scripts (vBulletin) for example, have this functionality. Personally I find it to be useless, but a lot of my search engine results are the archive threads, so I haven't disabled it. What about you?
It's not good SEO. I want spiders and visitors to find all my content where it belongs, in the regular forums. Jim
I've kept it despite the SEO hit because some of my overseas members say it's faster for them to download.
Archive on for the two forums I don't care about SEO. Disabled for my SEO forum which I do care about. I only see the archive as duplicating content (if only even the titles through vBSEO). Threads are fine in their original format in their original location if appropriate attention is given to make sure the content is accessible.