There may well be a duty cycle
problem, but I doubt it. Older ignitions used a single coil of similar type
firing all 8 cylinders. I would be more likely to suggest it was a
"bathtub failure curve" failure of the solid state
"trigger" circuit.
Ah-h-h; and why would duty cycle not
have an effect on temperature and failure rate of the ‘trigger’
circuit? The solid state components do dissipate some heat, and the more
cycles, the more heat and other effects leading to failure.
Al G