As long as the archive is not viewable, I would support it. Posts in groups related to whether a specific user should be allowed to join should be confidential, regardless of whether the group is still active. Make an archive for those posts, sure, but ensure only mods+ can enter the archive.
I disagree. I recently bought a group off 630 and it was about videos and making them, and the group I want is a computer support group. How are the old posts related to the group I want?