Maximum vertical excursion |z_max| predicted for sequential SSPs born at 8 kpc at different Galactic evolutionary times as a function of their age, adopting Eq. (3) and imposing the conservation of J_z in the orbital integration (see Sect. 4.3). The colour coding indicates the values of the quantity. We note that Eq. (3) was retrieved for thin disc stars in the solar vicinity for APOGEE stars younger than 8 Gyr. The shaded region shows SSPs that are older than 8 Gyr, for which the use of Eq. (3) may not be justified.