Collectors: How do you manage your collections once you can no longer readily find the files you need?

I just passed 50,000 not too long ago, and I started looking into my options.

>Hydrus Network
I'm leaning towards it, but it really sucks that it duplicates your entire collection and wastes twice the hard drive space. Also I don't like how you can't open images in HoneyView or any external program; you're essentially limited to the program to view images. You also give up folders forever, so I can't go find it if I want to reference it somewhere.

>Just keep sorting in folders
This is a huge pain in the ass for big collections. I can never find a file I'm thinking of if I need it.

>Some tagging software
I have no idea where to go on this one. Do any of you do tagging? I want to do something like this, just keep all of my images in one giant folder and tag them all for easy reference.

What do you guys do? How do you manage your collections?