In comparison to some stashes I've seen mine is fairly small, somewhere in the range of 200 yards, not counting my scraps which probably add another hundred yards or so. About a third of what I have is fabric that I have purchased over the years and the rest is fabric that was gifted to me. Since I make either scrappy quilts or art quilts I like having a stash. It allows me to put things together in unexpected ways, sometimes it forces me to do so since I pretty much confine myself to using my stash. I don't have enough room to have a bigger stash, so I'm on the fabric moratorium, though I do occasionally fall off the wagon when I see some fabric that really calls to me.
Other than the occasional backing fabric or if there really isn't enough of anything in my stash that will do for borders or binding, I have never purchased fabric with a specific quilt or pattern in mind because I don't work that way. I tend to purchase fabric based on what I'm running low on in my stash--- usually solids or patterns that read as lights, sometimes darks. When I need to replenish those I take a trip to my LQS and root through their remnant bins.
Rob