I have never prewashed any fabrics and have never had an issue. I have 5 kids I do enough laundry hahaha, even though only 4 live here. I do however always use warm and natural batting and use a color catcher when I do the first wash. If it has red I use two. I don't know if the batting has made a difference on shrinkage but it's never been an issue. I agree I think its a personal preference. What kind of quilt are you making? I love to see patterns picked for boys!