I always wash my fabric as soon as I get home from my LQS.
I sew up the ends of the fabric so it doesn't ravel. Wash the fabric through a wash cycle. (Separate colors from the white/light colors.) And use vinegar in the rinse water.
I want to remove any excess dye and chemicals from the fabric.
I dry the fabric in the dryer and iron the fabric before adding to
my stash. This way the fabric is ready for my next project.
By washing my fabric I don't have to worry about formaldhyde outgassing. I store my fabric in metal bins, in the closet of my sewing room, so the fabric can breath and is out of direct sunlight. Welcome to quilting!