Left: luminosity weighted ages versus the simulation time. The solid lines indicate the mean value of for the 23 simulations and the shaded areas of the corresponding colours indicate the standard deviation. The colour scheme is the same as that of Fig. 3. Right: luminosity weighted ages versus wavelength (black) for a simulation age of 790 Myr. The values for the Lyman continuum and the TIR at 790 Myr are also indicated. For comparison, the corresponding values for a constant SFR over 1 Gyr shown in Fig. 2 is indicated in dashed lines.