Variations of the quantities (top panel) and Ṁ_fwv_fw (bottom panel) as a function of the dimensionless time parameter τ = t∕10³ yr. These quantities are adapted from Paper I and linked to the parameters of a post-AGB model of 0.595 M_⊙ whose evolution speed across the HR diagram is increased by a factor of 5.5 (see text for explanation). The thick lines indicate the domain where the evolution of both quantities is well approximated by a linear fit (dashed) in the log-log plane.