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tokens: CO , CO and [OI] 63 m, respectively. However, the CO mm-line fluxes do not fully converge to the results obtained by the time-independent reference model, see arrows on the r.h.s. of Fig. C.1 , even for integration times as long as 10 Myr. This is consistent with the very long chemical relaxation timescales we find for those lines, namely 20 Myr, 50 Myr and 100 Myr in the line forming regions of CO , CO , and CO , respectively. The difference of the CO concentration between the Myr disk model and the time-independent reference model is shown in Fig. C.2 . All upper disk regions have practically indistinguishable CO concentrations, however, in the dark icy midplane (vertical visual extinction ), CO cannot freeze out directly where the dust temperature exceeds about 20 K (at radii AU in this model). Instead, the CO is very slowly dissociated in these regions by reactions with He created by cosmic rays. Most of the liberated oxygen atoms re-form CO, but a small part can form other molecules with higher adsorptions energies like water, and these will freeze out immediately. This mechanism provides a slowly ticking chemical clock in the dark midplane regions of protoplanetary disks, leading to gaseous carbon-to-oxygen ratios on Myr timescales between the water and the CO ice-lines, and to on even longer timescales, see ( Öberg et al. 2011 ; Helling et al. 2014 ). The (sub-)mm CO isotopologue line fluxes are somewhat affected by these differences, for example remainders of cold gaseous CO in the dark icy midplane can partly re-absorb the CO line photons emitted by the warm surface of the disk on the opposite side which cross the midplane. In this way, the CO isotopologue line fluxes of the time-independent model can be up to 30% larger than those of the time-dependent models. However, these effects are small compared to the impact of disk mass, size and shape, dust size distribution and settling, and the dust/gas ratio, and negligible for most optical and near-IR to far-IR lines. We conclude that the emission lines of chemically robust gas tracers, such as CO, H and the oxygen atom, are little affected by time-dependent chemical effects in our models. Disk evolution will rather have an impact on those lines via the changing stellar parameters, the changing shape of the disk, and physical gas and dust evolution. See e.g. Akimkin et al. (2013) for time-dependent disk models which include those effects. Appendix D: Properties derived from the model The mean gas temperature in the disk , the mean dust temperature , the near-IR excess, the m SED amplitude, the dust absorption mm and cm-slopes , and the millimetre and centimetre flux-slopes , are calculated as where is the gas mass density, the dust mass density, the local dust-to-gas mass ratio, the volume element, the distance, the spectral flux per wavelength interval, the flux from the naked star and the dust absorption opacity . Appendix E: Fluxes of optically thick emission lines It is noteworthy