It's fine to build a stash if you get a smoking deal on fabric at a store or come across a yard sale, but it's also important to remember that trends change and every year there are new fabrics to drool over. And that will never change.
It's a good idea to have something in mind when you buy it or you'll be wondering what you were thinking when you see it again later.
And I'm with the people who say it's not good to use others' volumes of fabric as your guide.