  Gravitational-wave detections are now probing the black hole (BH) mass
distribution, including the predicted pair-instability mass gap. These data
require robust quantitative predictions, which are challenging to obtain. The
most massive BH progenitors experience episodic mass ejections on timescales
shorter than the convective turn-over timescale. This invalidates the
steady-state assumption on which the classic mixing-length theory relies. We
compare the final BH masses computed with two different versions of the stellar
evolutionary code \texttt{MESA}: (i) using the default implementation of
\cite{paxton:18} and (ii) solving an additional equation accounting for the
timescale for convective deceleration. In the second grid, where stronger
convection develops during the pulses and carries part of the energy, we find
weaker pulses. This leads to lower amounts of mass being ejected and thus
higher final BH masses of up to $\sim$\,$5\,M_\odot$. The differences are much
smaller for the progenitors which determine the maximum mass of BHs below the
gap. This prediction is robust at $M_{\rm BH, max}\simeq 48\,M_\odot$, at least
within the idealized context of this study. This is an encouraging indication
that current models are robust enough for comparison with the present-day
gravitational-wave detections. However, the large differences between
individual models emphasize the importance of improving the treatment of
convection in stellar models, especially in the light of the data anticipated
from the third generation of gravitational wave detectors.
