I prewash everything and rarely starch. I tell my students to either prewash everything for a project or not to for the entire project. I've had bad experiences with not prewashing. If there is any shrinking I want it done before I have pieced, sewed and quilted. I don't like kits bc it's hard to prewash tiny pieces. I had one kit that I did prewash the pieces and one pieced shrank and raveled so bad that I had to substitute another fabric. If I had not prewashed would that fabric have ruined my project? I don't know, but I'm not willing to take that chance. Again. It's your quilt, your fabric and your time, do it the way you want to.