The reason you at times hanging on lines is for display, they are dry and not usually left long- a wet quilt weighs much more than a dry one and puts a lot of stress on the seams/quilting so laying your quilt flat would be the best way to dry it. On a nice day lay out a sheet, lay the quilt on top of the sheet then cover with another sheet (to protect from birds/critters, and sun) every once in a while turn it all over. I launder all of my quilts, wash & dry them as needed