I guess it would depend on which add-ons you're using. Any add-on that likes to store a lot of data (e.g. auction add-ons (I'm looking at TSM like you mention in the other thread)) will eventually build a large database that takes a bit to load (especially if you're running it on each of your characters). I don't think WoW's cache folder actually caches add-on data since add-on data is stored in your WTF folder, but I could be wrong.