I didn't start to build a stash, it just happened. If I'm buying for a specific project, I buy the recommended yardage plus an extra yard to yard and half. I've learned the hard way that some cutting measurements are wrong and have run out of fabric just to discover that the seller has no more in stock. If you have some left over, you can use for other things. To buy a fabric because I love it, it depends on price and how much I love it. If it is a large print and I love it, I will buy two or three yards. Large prints are great for fussy cutting or stack n whacks and require more yardage. I usually buy half yards and fat quarters for everything else. I impulse shop unfortunately and while I might have a vague idea for the purchase, by the time I get around to it, I've forgotten what I planned for it. This isn't necessary a bad thing as I love scrappy quilts. I don't buy border fabric until the quilt is together. I've bought border fabric I thought would be perfect and didn't use it. It's still in the stash. Good luck and enjoy!