For the video list post when starting a new thread:
Delete "old" videos to make room as necessary for new videos.
If there are no more "old" videos to delete:
- take all the "new" videos and save them in a list in a rentry
- add it to the "Previous lists" in this rentry with date (possibly creating a new rentry that is a copy of this rentry but with the new list added)
- update links to rentries in the OP and other posts as appropriate
- mark the previous "new" videos as "old" in the video post
This way, OP does not need to know an edit code to make "changes" and archive old videos, since changes are made by making new rentries and fixing links as appropriate.