I believe in retiring quilts that are to "ragged and torn" to continue using without causing more damage. Fortunately I have personally only had to do this one time, so far.
I had possession a family quilt dating from the last half of the 1700s that was "dead on my watch" by the time I received it. I donated this quilt to the textile museum at Colonial Williamsburg in 2002 because it was in a too poor condition to keep at home with the historical value in it. They were the ones who dated it.
It is one of two Virginia quilts in their collection from this period and the only one with written provenance, They tell me it will likely never be displayed, only preserved for research, due to the condition.
The background of plantation-grown flax, spun into linen fabric, is still strong, though it shows evidence of very old repair (Civil War damage???). But the brown English chintz and calico in many the blocks was likely mordant-fixed with iron and the threads are disintegrating in many places. The hand quilting was likely done with linen thread because it, too, is holding up quite well. But, in general, the quilt was too old and too unique to keep safely at home for personal use. I was so glad I was living in Williamsburg, VA, at the time because that was the perfect permanent home for this "used up" quilt.
Jan in VA