Hmmm how to build a stash. It just happens. If you ask my DH, he would swear the fabric breeds in the cupboards. I buy what I really like. Fabric really does talk you know.Some of it even shouts. When that happens, it needs to come home with me.
Sometimes it has a specific reason for coming with me, others just because I like it. Of course, there's also the planned overs from other projects. I always buy too much, so I plan to have "overs". It's a bit like the Pantene ad, it won't happen overnight, but it will happen.