Well...I've have fabric that I've bought from So-Fro fabrics (remember them?) 22 years ago, Ben Franklin, Walmart, and JoAnns, and they all are crisp and sharp as the day I bought them. Some I prewashed and some I did not. I've always stored them in those clear rubbermaid totes and put them in the closet or corner of my sewing room, away from any light.
Maybe it's not where you buy them but how you store them?
Just a thought...