Usually purchase for project in mind. I always buy more than stated and I rarely buy fat quarters as I find few patterns which require 1 fat quarter a 1/4 yd is more useful. Don't forget if you want red the red in the stash will not be the correct shade . Always an excuse to go shopping. It i think also depends on your location and weather conditions do you need a collect because you will be blocked in or distance too far. These would be my main concern. I have just organised a delivery of fabric for me to use over Christmas when shops will be closed for a week.