UPDATE: After 18 months, the black band is finally ready to snap in half.  Time to order new ones.  I will look for something more durable.  I guess you get what you pay for.  I rarely have used these -- they just seem to get bad with age, which makes sense for essentially giant rubber bands eh?  Maybe this is the way it is with bands, but it gives me pause as I think about life on the road depending on these things for my workouts.