My category numbers go up to 394 - however if you go to my root
http://www.nonleague.com you will only see three categories - all the others are controlled via pull down menus or other links.
Means that you can have a large number but not swamp the index page, and put people off - plus even if several are virtually empty it doesn't matter - as they are hidden from view unless the user selects that particular combination of forums.