I buy for the project, never for stash. Now sometimes a fabric just doesn't work out the way I thought it would, or I need a lot less than I thought, but I always buy with a project in mind and I limit myself to only buy 1 project ahead. I live in a tiny space and while I love scrap quilts I don't have room to store any excess yardage. After every couple projects I do something scrappy to keep the stash down.