No. The cleaning out of this data doesn't help performance all that much. It just hurts it when I actually am performing the clean-up.
The clean-up itself is a heavy hit on the server. But once done, things return to normal.
The only way I can see to significantly impact performance by removing data would be to remove years of posts, which I don't want to do unless we absolutely get to a point that we just have too much. THen I could make an "archive" forum or something like that. But I think we've got plenty of time before that will be needed (a good year or two, I'd say).
If I do any of the more regular cleanup again, I'll put up the "Site down for maintenance" page like it automatically does during backups (which run around 2 or 3am PDT). This will both avoid concern that it's an unknown issue, but also speed up the actual process of cleanup.
-Alex