For every project I either wash ALL of the yardage or I don't. If there are no worries about colors bleeding I tend to not prewash. If there are intense colors in the lot, I do a color test with Q-tips or a scrap of fabric in a hot water glass with detergent (generally a small piece will indicate if it's going to run). Then I make my decision. IF I prewashed all the fabric I tend to throw the finished quilt in the dryer with a damp tower to get the errand cat hairs off and freshen it up. IF I didn't prewash, I will wash the quilt with color catchers before gifting it. Better safe than sorry.