In combination with two alternating junction temperature swings designed for equivalent theoretical damage contribution, a lifetime reduction of 23% compared to Miner's rule prediction is observed. Insights in the experimental methodology as well as statistical, degradation, and equivalent-stress analysis results are presented. The approach enables further innovation due to revealing critical sequence-interaction effects in applications such as electric mobility, renewable energy systems, HVDC transmission, and other power semiconductor-based converters operating under realistic mission profiles. This paper showcases its capabilities through a statistically validated (p = 0.0003) demonstration that classical linear damage-accumulation models significantly overestimate IGBT module lifetime under alternating stress conditions.