You know how they say you should store your fabrics and quilts out of the sunlight? Well, let me provide a brief illustration of what happens when you expose your fabric to a whole lot of sunlight!
The closet in which I keep my clothes has a window. A south-facing window (LOTS of intense light).
When I first moved into this apartment, I knew that I needed to put in a curtain to block the sun. I ended up using a bit of quilting fabric.
After five years, this is what the fabric looks like:
Can you imagine if this fabric was part of a big stash that had been folded and stashed in a sunny place?
That could be truly, epically bad!
If you have a sunny sewing room (I have a dim corner or an office!) Get doors for your shelves or a cabinet or something.