Molecular gas depletion timescale (left) and molecular gas mass fraction (right) as a function of the redshift of our galaxies shown by the red filled circles. Similarly to Fig. 4, the dotted red segments represent the range of possible t_depl and f_molgas measurements of our galaxies as derived with CO-to-H₂ conversion factors sampling values from ${\alpha }_{\mathrm{CO}}^{\mathrm{SB}}=1M_{\odot }{(\mathrm{K}\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{pc}}^2)}^{-1}$ to ${\alpha }_{\mathrm{CO}}^{\mathrm{MW}}=4.36M_{\odot }{(\mathrm{K}\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{pc}}^2)}^{-1}$. The t_tepl and f_molgas means, errors on the means, and standard deviations obtained for the CO-detected MS galaxies from the compilation of Dessauges-Zavadsky et al. (2020) are shown by the black/grey crosses in five redshift bins 0 < z < 0.1, 0.1 < z < 1, 1 < z < 1.5, 1.5 < z < 2.5, and 2.5 < z < 3.7. The light-grey shaded area corresponds to t_tepl and f_molgas derived by Béthermin et al. (2015) from the FIR SED stacks of MS galaxies. For all MS galaxy measurements compiled here, the same ${\alpha }_{\mathrm{CO}}^{\mathrm{MW}}$ conversion factor is assumed. Our extreme starburst galaxies have significantly shorter t_depl than those measured in MS galaxies at any redshift (left). This indicates that they are vigorously consuming their molecular gas mass reservoir to build up their stellar mass. On the other hand, they have very high f_molgas (right), in excess with respect to MS galaxies at similar redshifts, showing that their mass remains dominated by the molecular gas mass over the stellar mass.