[ceratopisan]

Outside of this not-really-helpful study, I can say that sourdoughs do tend to have a longer shelf life without preservatives; they resist staling and mold better than white bread, all things being equal. Commercial bread usually has preservatives added to balance this out, but it won't work out the same.

I've found sourdoughs, especially big miches, will actually taste better after 2 or 3 days. Commercial packaged breads are usually a straight downhill slope.

Source: direct experience, various baking books, historical info.