For me it's simple. If I love it - gotta have some. If it's just blenders I'll buy a 1/2 or a yard. If not, and I have money I get 3 yards. If I don't have much money, but still gotta have some, I get what I can afford at the time. If I have a quilt in mind I buy all that I need for the entire quilt and some extra for mistakes or accessories etc.