My partner works at a restaurant where they serve sourdough as the bread you snack on to tide you over while perusing the menu. They are closed Sundays, which means any leftover bread on Saturday evenings goes home with the employees (since it can't be sold as day-old at the adjacent bakery the next day, as with other days). This means my partner frequently comes home with five or so loaves of sourdough.
Occasionally she'll also end up with a loaf or two of a different sort of bread. A nice wheat, or this particular bread full of nuts and herbs that they make.
It takes a long time for two of us to get through five large loaves of bread, so when she brings them home they go straight into Ziploc bags to keep them as fresh as possible for as long as possible. The sourdough loaves last positively forever (albeit with a little bit of loss of texture), but the wheat loaves or nutty-herby-loaves-I-forget-the-name-of always end up with mold spots after five days to a week.
I know nothing about sourdough bread other than that it tastes delicious. Is it more resistant to molding than other types of bread?