Proper storage of brownies & blondies: Will keep for 3-4 days, stored in airtight container at room temperature.
Shelf life of brownies & blondies: Shelf life change if there is cream or frosting on. In that case it must be kept refrigerated.
Freezing of brownies & blondies: Can be frozen for 4-6 months if well wrapped in cling film and aluminum foil.
Defrosting of brownies and blondies: 3 hours before serving, remove the cake from the freezer and unwrap the tinfoil. Let thaw at room temperature.
How can you tell whether they are good or bad:
Mold, bad taste or strange texture. If you doubt, leave it out.