Generally speaking the forum runs absolutely fine these days, and any issues it has aren't due to the number of rows in the tables. There are countless old classic threads people enjoy reading that have been locked, so people can't even bump them up to make them stay.
Disk space is practically free these days, I don't see the need for auto-deleting them at all; there's never any new content appearing anymore as everyone assumes it's already been covered, it's just the site slowly committing suicide.
Basically - there is zero need to auto-delete old threads. By all means in time you could have it that any thread with more than five thanks gets kept and the rest get deleted or something, but until then can we please just disable the deletion job?
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