@donho ,
Makes sense.
Since deleting posts was tedious for me, I had recently been looking into whether I could use the API that the forum offers to write a script to automate some of the cleanup (like with purging the deleted posts/topics), but that will take some time to develop.
update: As of Nov 9, the purge automation is working, and it will run once a week. (Along with purging deleted posts/topics, it will also delete user accounts that are more than a year old where the user never posted and never logged in after the first day – nearly half of the 30000 accounts were in this category)