Monte Carlo simulation of a population of nine galaxies (thick stripes) with successive active and quiescent phases. We mark the active phases (thin stripes). Each galaxy spends a different fraction ϝ_a of the time in the active phase. We model the time spent in both phases as draws from exponential distributions: t_a ∼ Exp(λ_a) and t_q ∼ Exp(λ_q). We assume that all galaxies share the same quiescent phase rate parameter λ_q = 10 Gyr⁻¹, although this may not be entirely correct (Turner & Shabala 2015). This assumption fixes the active phase rate parameter: ${\lambda }_{\mathrm{a}}=({ϝ}_{\mathrm{a}}^{-1}-1){\lambda }_{\mathrm{q}}$. On human time scales, we can access only a snapshot view of this population. During the present snapshot (vertical line), seven galaxies generate RGs, and could be included in an RG sample. RG ages at the snapshot (hatched parts of the thin green stripes) generally increase with ϝ_a.