When choosing what sock wool to use, or what book to read, I often choose the newest I've bought. After all, I buy a book because I want to read it, so I'll read the most recent book first. I use my Kindle as metaphorical book pile: I only have books on it that I (think) I'm going to read, and as soon as I have finished reading a book I delete it. I currently have twelve books on my Kindle, and am making a conscious effort to read the books that I put on there months ago, rather than the most recent.
And I'm feeling the same about my sock yarn. This is a pile of lovely yarn (with the possible exception of the beige ball on top - I might overdye that) that I've had for over two years. The pretty blue yarn I've had for longer than I've been married.And, even though the yarn is lovely, it's never going to make it's way to the top of the pile if I keep buying more. This isn't about reducing my stash, as such. It's about giving every ball of yarn in it the chance to find it's destiny, rather than languishing in the bottom of my stash box.