I only prewash batiks and fabrics that may run on the first wash (reds and hot pinks usually). I never wash a finished quilt before giving it away unless it has dust or some other schmutz on it (I don't have a pet). I have a front loading washer and only wash quilts that are throw sized or smaller in it. I feel it doesn't use enough water to do a bed-sized quilt without the chance of colors running. For those I use a commercial big washer at the laundromat.