Answer
Life is counted in cycles, not in years, and it is governed by operating stress. For wave springs the accepted method is to calculate a fatigue stress ratio from the material’s minimum tensile strength and the stresses at the two work heights. Published industry guidance maps that ratio to expected life: roughly 0.40–0.49 corresponds to 30,000–50,000 cycles, 0.61–0.67 to 100,000–200,000 cycles, and above 0.70 to more than one million. Static applications may run to 100 % of minimum tensile strength; dynamic applications should stay below 80 %. A spring designed under its endurance limit is effectively unlimited, and one designed above it will fail on schedule — which is why the required cycle count belongs on the drawing alongside the load.
