Bearisgray, I've wondered the same question you posted many times! but my answer has turned out to be pretty much like LI diva's. I prewash as much as practical for any fabric that will go into a quilt I expect the user to be washing, hoping it will shrink/bleed less for the end user. I'm a new quilter and only made 5 quilts so far. I haven't washed jelly rolls because it seems like they'd just end up a frayed mess. I figured, if a good portion of my quilts would already be preshrunk, it wouldn't be the end of the world if some jelly roll bits shrunk a little after the quilt was finished. It turns out that in the quilts that have both jelly roll (not prewashed) and yardage (prewashed) intermixed -- after washing the finished product, it's just fine! The quilt is still straight, the jelly roll parts aren't apparently shrunk out of proportion to the prewashed parts. So, I'll keep on prewashing stuff FQ or bigger, but not worry about prewashing tiny precuts.