Our estimated depletion timescale, τ, with respect to the compactness, C, of a gaseous stellar cluster of any total mass. We considered three possible star formation efficiencies, ε. Each sub-figure (a), (b), (c) corresponds, respectively, to solar, subsolar (~0.1 Z_⊙), and low (~0.01 Z_⊙) metallicity. We assume that at subsolar metallicity PPISN operates, and that in the low-metallicity case both PPISN and PISN do.