Poser 6 and assumedly Poser 7 allow multiple Runtimes.  With this feature and some time you can divide your content into categories, each category being its own Runtime.  Right now I have three Runtimes.  The base P6 Runtime which only has what P6 came with in it, then my new stuff Runtime and then my old P5 Runtime.  Poser 6 always loads the last Runtime you were using (though there might be a way to change this, I just haven't looked yet).  Instead, I always make sure to switch back to the P6 runtime before exitting.  It starts up so fast now, that I'm often surprised.

It does take it's time when I go to open my huge P5 Runtime, but then it seems to swim along with the browsing much smoother then P5 did.

Still, I intend to break my content down to categories because as Sparrownightmare pointed out, there are just too many cryptically named things.  I also have a big issue lately forgetting which piece of clothing goes to which character since most clothing don't even give a vague clue in there thumbnails.

I'm figuring on dividing clothing and morphs by character, and then having Themed runtimes for props and scenes, like Sci-Fi, Western, Fantasy, etc...

Yeah, It's going to take time, but it will be worth it.