Sometimes I do, but usually not ... it depends on the fabric, how it feels and whether I think the color(s) might run; usually, a small scrap of fabric wetted and laid on a paper towel to dry tells me if it is color fast. I always measure and wash flannel until it stops shrinking. Also, I totally miss the point of washing quilt fabric in hot water; washing completed quilts in hot water should be avoided IMO in the same way that washing woollens in hot water should be avoided (as the wool obviously will shrink).