There are a few common reasons why the layers of a quilt can separate with use and washing over decades. From my experience, natural wear and tear on the fabrics is usually to blame. Cotton and other natural fibers will weaken and become brittle as they age. The repeated stress of being washed and folded also takes its toll on original stitching. Another culprit is moth damage – even if you don’t see active infestation, moths can chew on fibers in hidden areas and cause layers to detach.