in my home, most survive the trip from the oven to the drying rack. fewer survive the journey from drying rack to plate. none last long enough to make it to the refridgerator. hypothetically, in the refrigerator they would last around 8 days if covered with plastic wrap.
butter lasts muchmuchmuchmuch longer, so your best bet is to make only as many as you plan on eating in an 8 day period. who likes defrosted brownies? plus a too cold freezer will destroy the good stuff.
just a little tip, make sure you take them out of the oven at least 5 minutes before the recipe says so. they will be super moist and goey!