Why don't store-bought bread crumbs spoil? Can you make your own bread crumbs and save them for later use? Will homemade breadcrumbs mold?
Bacteria need a friendly environment to live. They can't survive without mosture. Mold tolerates more, but it needs moisture for life too.
Bread is too dry a food, so it doesn't catch bacteria. This is why it can be stored outside the fridge. But if you live in a moderately humid climate, it can still be moist enough for mold to grow, especially if stored in a non-breathing package (plastic bag). Drying the bread to the point where this won't happen is possible, but it gets quite hard then. Examples for such dry bread are zwieback or finnish crispbread.
Store bought breadcrumbs are dried to the point where they can't catch mold. This is why they can be stored for so long. If you make your own in the food processor, they will be similar to bread. Probably a bit better, because the bigger surface will let them dry quicker than bread. But if you want to be sure they will last, dry them. You can use a dehydrator or put them in the oven at the lowest temperature (usually.50 deg C) and hold them there for 4 - 5 hours.
Agree with the first answer. I would like to add that drying out your bread crumbs in a slow oven or dehydrator also serves to kill bacteria and mold spores that may be present so that they remain good to use while they are stored in a clean sealed container. They will eventually go rancid from the oils present from the original grains used to make the flour, but that will take quite a long time and is not unsafe but merely spoils the flavour of the crumbs.