I'm not a 100% prewasher. Most of the time I don't but if I'm using some fabrics like red, etc that could run, I was them. I only prewash flannel if the shrinkage will effect my project, like in a rag quilt it won't hurt. If I were making pj's then I'd wash them. I wouldn't wash precuts even though I've seen those who do. If you don't think any of you fabric that you are cutting will fade then don't worry about it. My thinking is; when you go to a class where everything is included, you know the ones holding that class didn't wash and iron all of that fabric. Yes, you could get some fading or shrinkage but so far I've been lucky just sticking to my rules. I do also prewash batiks.