I did a pieced baby flannel quilt and did not prewash and it was a mess when I washed it in cool water and dryer dried it-- all the fabric was LQS and some pieces shrank and some did not. Tossed it. I have had some LQS flannel that did not shrink at all and some that lost several inches -- if the fabric came from JA's the shrinkage was worse.

Just because a LQS has it doesn't necessarily mean its good quality.

There are other reasons to prewash besides shrinkage. Once a member posted here that she hit her brand new un-prewashed high quality fabric with the steam iron and a toxic gas cloud came from the fabric that caused chemical burns to her skin and affected her upper respiratory. I don't think she will consider prewashing a waste of time after that horrendous incident.

The majority of fabric is manufactured overseas and treated with many harsh chemicals to keep vermin and insects from wanting to get into it while it sits in storage containers at piers and on ships. Others are treated with sizing to give it a nicer "hand". Formaldehyde is a very common chemical applied to fabric as an agent to prevent wrinkling, give a better hand, reduce static etc.

One member reported seeing a child in a quilt shop wiping their hands after sneezing on the fabric sitting on the shelf.

Of course it is the end users decision. Many prefer to work with un-washed fabric. Others like Bree and myself have chemical sensitivities and then there are so many of us, (myself included) that started working with fabric by sewing garments and prewashing was drilled into us by home-ec teachers. So despite my chemical sensitivity which developed only within the last 10 years or so, my prewashing habits were already deeply ingrained.

And that is why I prewash flannel - twice. Other fabrics are prewashed once. If they aren't prewashed before I work with them than the chemical sensitivities make me miserable.