Time evolution in Model QA10x2 of (a) the mass fractions of the diffuse ( f _diff, solid) and GBC ( f _GBC, dotted) components, (b) the mass fractions of the cold ( f _c , dashed), unstable ( f _u , dotted), and warm ( f _w , solid) phases within the diffuse component, (c) the density-weighted vertical scale height H, and (d) the SFR surface density Σ _SFR. The initial increase of f _GBC and f _c stops at t = 0.1 t _orb = 22 Myr when the first SN event occurs inside a massive dense cloud. The model reaches a quasi-steady state after a few tenths of an orbital time, in the sense that the physical quantities fluctuate but do not evolve secularly. Note that f _diff is positively correlated with H.