Evolution in time of the same final halo of Fig. 1, but using our new model with a_g = 0.04 and γ = 2. Left panel: the relative growth rate does not reach a minimum, nor does it reach negative values. This implies that the shells grow at all times, but as the central panel shows, the mass growth history for the shells flattens out towards the end. The behaviour at the virial radius follows closely (but not exactly) the Wechsler model, as shown by the dash-dotted curve. Right panel: mass profile at different epochs.