I can see how too long an elbow would be bad news for spoke life. This raises the question of how much variation is found in hub flanges, since the proper elbow length would be a function of flange thickness. It seems reasonable that if you had a hub with really thin flanges, you would get better results from spokes that fit better in this regard, even if they were of older vintage. I can image spoke manufacturers cringing at yet another variable, and hoping to take a one-size-fits-all approach with regard to elbow shape.
This is an example of how good design requires optimal compatibility of all the components. Everything has to fit together and work together just right, and even in something as simple as a bicycle wheel havoc results if just one variable is changed at random.
John Hurley
Austin, Texas, USA