Number of planets left in the systems as a function of time. Dotted line corresponds to the face-on assumption (simulation 1), solid line to the inclination inferred from observations (simulation 2), and dashed line to the largest separation achieved from inclination (simulation 3). See Table 1 and Sect. 3 for descriptions about the simulations. The age estimate of HR 8799 ( Myr) is indicated with a solid line with the grey region corresponding to the uncertainty.