I always cringe a little when people say they use Sharpies on quilts, or permanent markers. They really aren't and will bleed into other fabric and if writing with them on fabric they will bleed and get fuzzy and faded.
I had the opposite happen to me. I used an expensive pigma pen to write a quilt label for my DD's quilt. The label has faded out. I had to do another one. The label I made for my niece's quilt I used a Sharpie thin line maker. That label hasn't faded at all. Both quilts are about the same age and the Sharpie label gets washed much more then the Pigma pen one.