I used hundred year old+ fabrics to piece a quilt for the friend who had given them to me. I found them inconsistent in weave, thread count, quality, and hand. Difficult to work with as I had literally scraps and had to recut/resew/piece some to make the blocks. Some were stiff, some were very thin or loosely woven, most were what we'd call poor quality today.
I've also shopped vintage fabrics (over 75-125 yo) at Houston and Mid-Atlantic Quilt Shows and found them to be very expensive, naturally, if they were in good enough shape to want to quilt with.
Even though my interest is antique quilts, quilt history and restoration, I personally do not collect or use actual vintage fabrics very often. Our current mills are doing an amazing job of reproducing the actual colors and prints of mid-to-late 1800s and 1930s in a "hand' we can use safely today.
Jan in VA