I saw an article about this many years ago. A quilter compared torn fabric edges to cut fabric edges under a microscope. She was horrified to find damage to the torn fabric that extended at least 1-inch, often 2-inches, and occasionally 3-inches in from the edge. These areas would be the first to weaken and give way in a quilt, and she wanted her quilts to last for many decades, so she went to her stash and cut off all the torn edges of her fabrics 3-inches in.
Does anyone here have a microscope? I'd be very interested in checking this out myself if I had a microscope!