largest is about 13million posts..... the one I'm provessing now is about 4.5M and had a nearly 7Gb DB... I've already trimmed 3.5Gb and its still rolling....
This mod is ONLY for the super big I guess

I have the archive set by date so that you can archive based on date. I'm finding 200 days back is a good way to handle it. I'm unsure of load and things like that... I won't know till next week.