Various timescales as a function of ambient density for our simulated sample of SNRs. Uncertainties arise due to the finite spacing of the snapshots and due to the choice of Z_{ej, thr}. The timescales of shell formation, the end of the PDS phase and SNR implosion agree well with the predictions from models based on simulations of isolated SNRs (Kim & Ostriker 2015; Romano et al. 2024a). The timescale measuring the onset of star formation within the SNRs is within a factor of 5 of 10 percent of the free-fall timescale of the star-forming SNRs.