Originally Posted by Jobst Brandt
The idea that spokes are not strong enough is based on failures of
spokes that were not stress relieved after building the wheel. For
wheel builders who cannot understand the concept and refuse to take it
on faith, thick spokes are the only answer... this in spite of many
failures among 2.0mm diameter straight gauge spokes. That's why we
have 2.34mm diameter spokes and on the other end, "Revolution" spokes.
Spokes (Jobst Brandt)
It turns out I was echoing Brandt's sentiments on why spoke elbows fail - they weren't stress relieved, "bent" or "seated" to the flange and end up flexing until they work harden. Hence his dismissal of the 2.34 section spokes.
I don't think any reasonable spoke in a wheel with a reasonable spoke count has any reason to fail from mileage alone, IF it is stress relieved correctly when built. Brandt would wear out multiple sets of rims on one set of 1.8/1.6/1.8 spokes with the only breakage coming from foreign objects.
My personal theory as to why butted spokes are "stronger" is that they move some of the spoke flex from the (unseated) elbow to the thin spoke section which can handle it better. That way the unseated elbows don't work harden as quickly from the tension cycles.
It would be interesting to build a front wheel with Revolutions (2.0/1.5/2.0) on one side and similarly light 1.8 straight gauge on the other and see if there is any difference in longevity. They both would weigh about the same, but have that mass distributed differently.