We always tied our quilts. When the outside needed washing (not every year), the ties were cut off, the outside was washed and then it was all put back together (after any needed repairs. Later we found it was better to have the wool batt encased in cheese cloth or other light weight fabric. That way the batt had less chance of shifting and producing spots with almost no batt left.
We always tied with wool yarn. Those ties got tighter and tighter the longer they were on the quilt.