When I worked at a quilt store up north, we experimented with this. We had been getting our bolts of Benartex flannels and they came with cards that said "colorfast - no need to pre-wash!" We tested it, and sure enough... they didn't bleed. But they shrunk from 43" to 39". We tried several pieces. When we attended quilt market, we asked the Benartex people about it and they said, "well, most people are only concerned with bleeding." And then they tried to tell us that when people make flannel quilts they like the puckery look, yada yada yada... We were NOT impressed.