I'm fairly new to quilting, have made a sampler, a couple of wall size, and a lap top. I did not wash the first three, figuring they are on the wall and could be dusted. I washed every piece that went into the lap top before I sewed it, and again after.
I almost messed up though! A friend gave me a couple of nice red colors I used for the birds in the quilt, and I almost forgot to wash them! Small sized, I put them in a bowl with vinegar and the water turned red! I'm so glad I did, it could have ruined the 80 hrs of work I put into that quilt!