Redshift evolution of the growth time as a function of SMBH mass. In each panel, the horizontal dotted line marks the age of the Universe at that redshift. Lines indicate the different values of ϵ: black, red and green lines are for ϵ = 0.05, 0.07 and 0.1, respectively. The main epoch of growth is at 1 <z< 3. At later time, only low-mass SMBHs can be actually growing in mass, while at earlier time only in the model with ϵ = 0.05 the growth time is much lower than the age of the Universe.