Most of the places online that I shop have a 1 yard minimum on sale fabrics - so that is generally what I will buy if I don't have a very specific project. If I can I don't like to buy backing until I've gotten enough done on the top to have a good idea of what I want - then I get to shop some more. I have several 5+ yard pieces of potential backing that is languishing in my closet. I don't design a quilt around the backing, so have found that for me, it is not a good plan.