The recommendation Is at least every 4", more is OK, less is risky. If the item will be laundered and you have not done the minimum amount of quilting the batting will separate and ball up so there will be areas with no batting and areas with globs of batting. The recommendations are the minimum amount of quilting required. You ( might) be able to get away with less if you use a batting with scrim like warm & natural that allows up to 10" between quilting lines