I seldom prewash the fabric for any quilts. I don't lock the stitches either. Just line them up and sew them. I use a decorative stitch for the outside border. They last forever through many washings. I usually wash them at least 4-5 times before i give them away. That way most of the fraying takes place and they look great. Remember to clean the lint filter after each washing! The first 3-4 washings have a lot of lint and threads.