I wash every quilt as soon as it's finished to get the starch out and leave it nice and clean. However, if your quilt has no issues that require washing then you don't need to do so. Reasons to wash would be if there are quilting marks that need to be removed, if the quilt is dirty or has an odor (such as from smoke or pets), or if the quilt isn't quite flat and square and would benefit from blocking. The reason not to wash would be if you don't want the batting or fabrics to possibly shrink up, or if you're worried about the colors running in the wash. I don't think the judges would grade a quilt down because it has or hasn't been washed.