Sorry, Sam, I just reread my post and I shouldn't have said "...has always been..." .  Should have said "...in many instances...".  That's what I get for not proofreading my responses.

If you can, cohesively, organize one runtime for easier access of all content, then it might be to your benefit.  As Sam indicated, if the folder becomes too large, loading time could increase substantially and slow down your application.  However, I have seen a substantial improvement with the most recent Poser iterations.  And the new library format in P8 and PP 2010 is a big improvement whether you like it or not.  My philosophy has been to install your content, use it for whatever projects are on your list, then uninstall it.  The rule that has floated around for ages, if you haven't used it in 6 months, the likelihood that you are going to use it again anytime soon, is very low.  Maybe Cyberwoman should do is take a content inventory, determine the degree of importance for each, and delete the unnecessary.  Not only would the runtime folder weight lighten, there would be less content to organize, and a better opportunity to properly separate new content.