Theraband Loops are a tool we use for much of our low back, hip and knee programs. When used around the knees it gives great feed back to the hips to promote external rotation, which is a major training goal to rehab and prevent injuries to the hip.
We use around the ankles when activating the gluteus medius and lateral hip muscular as well. As for durability, I have had some of the same bands used multiple times a week last for more than 2 years. Most people use the blue band.