I actually just finished quilting a quilt using my walking foot. I set my stitch length to 3 because I thought the stitches were too small at the factory pre-set 2.5. It may just be a matter of personal preference. Even if there were rules (which I don't think there are),I would still do what I think looks best and what I think suits my own needs. In other words, if you would like longer stitces, GO FOR IT!!!