Evolutionary stages of a 15 M_⊙ star with 5 Z_⊙ modeled with MESA. Panel a): H–R diagram, with key evolutionary points marked with colored stars. Panel b): wind-lifetime ratio vs. mass (one of the tracks from Fig. 1), with the same evolutionary points marked. For this example system (and indeed all other systems), the steepest wind-lifetime ratio decrease occurs when the star halts core H burning and begins He burning. We note that the He burning shown here (marked with the red star) represents the first instance of a decrease in total helium mass, and precedes the core He burning defined in Hurley et al. (2000).