  We calculate volume-independent ratios of cumulants of the net-proton number
distribution up to sixth order in a fireball that cools down after the chemical
freeze-out. A hadron resonance gas model is used together with the assumption
of partial chemical equilibrium, which fixes the number of observed stable
hadrons after the chemical freeze-out. It is shown that due to only weak
departure from the statistical Boltzmann distribution, also the
volume-independent ratios of higher-order cumulants of the net-proton number
show only weak dependence on the temperature. This observation supports the
possibility to measure non-critical cumulants at chemical freeze-out even after
subsequent cooling in the hadronic phase. Cumulants of the net-baryon number
behave similarly, while those for the kaon number vary more strongly with the
temperature. Our results are relevant for the current fluctuation studies of
the RHIC-BES runs.
