I pink the cut edges, wash by hand with a color catcher and dry in the dryer. I then use spray starch while pressing to restore the fabric body for easy in cutting and handling. Very little trouble with threads, bleeding, etc. I am chemically sensitive and I can't work with most fabrics unless I pre-wash. If I did not have this problem, I would probably wash the quilt after it is completed. I think it is a matter of personal preference and/or necessity. There is no right or wrong.
mariah