Almost is not "They are indestructible", aluminum tubing can keep 3000psi at bay, but I can tell you after 22 years experience it does in fact fail and under normal operating conditions without outside factors it is indeed almost indestructible. I have also seen the grestest wire in the world at the time go from the best thing ever designed in aviation to the most dangerous material in an aircraft years later. The point is pretty clear, not all of the applications were thought out completely, you can only guess every condition, it is not until you apply it that you run into the ones you did not think of.