Luminosity weighted ages versus the wavelength for a constant SFR over 100 Myr (solid lines) and 1 Gyr (dashed lines). The magenta and red lines indicate the luminosity-weighted age for the Lyman continuum and the TIR for a completely buried galaxy, respectively. We see that the typical timescale probed is not only strongly dependent on the estimator and on the wavelength, but also on the SFH, with longer wavelengths and the TIR being the most sensitive to the duration of star formation episode in this simple scenario.