In combination with Miner's rule, power cycling lifetime curves for arbitrary junction temperatures are derived from only two standard reference curves, without additional test data. Insights in the model as well as a comparison with experimental power cycling data are presented. The method enables further innovation due to more precise lifetime estimation, optimized thermal management, and reduced design margins in applications such as electric vehicles and industrial drives with fluctuating loads. This paper showcases its capabilities for real-world junction temperature profiles with varying peak values, validated against measured power cycling curves.