Observed recurrence time evolution, overplotting some predicted evolution tracks due to gas drag and slowly evolving disk precession. Different lines are shown for different sets of parameters (as is shown in the legend), such as the spin (a_•), the proportionality constant between disk and star nodal precessions (α_LT), and the parameter η ≡ ΣR_⋆²/m_⋆. Variations in the slope of the calculated curves correspond to variations in the relative star-disk inclination, such that the plateaus (low Ṗ) correspond to when the star and disk are near alignment.