Why do North Charleston cleaners talk about a three to four day window?

Because that is the local physics in summer. The market's own copy states it directly: with June through August heat at 88 to 92 degrees and dew points in the 70s, fluids from an unattended death seep through subfloors within three to four days. Before that window, the job is often the room and its flooring surface. After it, the scope adds the subfloor, sometimes the joists and the crawlspace below, and odor treatment across adjoining rooms. The window is not a sales device; it is the reason the call after scene release is worth making the same day, and why the discovery date is a real input to the estimate.