Behaviour of the two different dust components (molecular clouds, MC; diffuse dust, DD) as a function of galactic age in units of the characteristic escape time from molecular clouds τ_esc. We assume an in situ SFH as the blue line in Fig. 1 and set the characteristic escape time to 5 × 10⁷ yr. Left panel: percentage of the intrinsic stellar luminosity absorbed by MC (blue), DD (green), and by both components (black). Right panel: temperature of the dust component computed from the age-dependent energy-conservation scheme implemented in GalaPy. The vertical dotted line marks the age, τ_quench = 8.8 × 10⁸ yr, of a possible abrupt quenching event; solid lines refer to the evolution with quenching, dashed lines to that with no quenching.