I don't have much of a stash. A couple of wide backs, a couple of 10-yard mini bolts of Kona snow, and some clear shoeboxes that hold the remains from previous projects. I tend to buy what is specifically needed for a project, maybe rounded up to the next 1/4 yard.
The only real "stash" I have is 100-needle packages of the 5 sizes I use most often, 3 for sewing, 1 for my serger, and 1 for the longarm.
I've been to enough estate sales around here to see all the outdated fabrics and notions that go unsold and think about the wasted money. Most of that stuff ends up in a landfill after being a hassle for the survivors to deal with.