HI-to-stellar and dust-to-stellar mass ratio as a function of light-weighted age. Orange and grey lines show fits to HI- and dust-to-stellar mass ratios for sub-samples divided into stellar mass (top row), the black hole-to-stellar mass ratio (middle), and redshift (bottom row) bins. Blue and red dashed lines show fits to the overall ETG sample from Fig. 2 and are given for reference.