I've mixed denim with flannel on several quilts. They make a soft cuddly quilt. The denim will last for approximately 17 centuries, so it will outlast anything. ha ha. But as long as you use good quality flannel, they wear about the same. Don't use that $1 stuff that walmart sells. I'm using one that I made in the mid 70's, and it's going strong! I keep it in our SUV for an unplanned nap now and then. S.