I can honestly say that I know what's in my stash (rulers, patterns, and fabric), but I have 2 advantages:
1. I've been collecting less than 2 years, and my stash is "only" one bookcase big (not including the scraps or packaged batting)
2. I'm a computer geek and I wrote a program to keep track of all of it: Fabric, patterns, notions (mostly tools), thread, books/magazines, even projects and equipment (info about all of the sewing machines, and last time serviced, etc). Then when I add to it, or I'm going shopping, I make pdf files to send to my tablet to compare with. It took me a few weeks of programming, and then another 2 days of photographing stuff, or finding pics on the internet and entering data and then folding all of the fabric on boards like AlaskanSunshine posted about here:
http://www.quiltingboard.com/tutoria...om-t43871.html.