[Unclenick]

The main advantage to shiny cases is the ease of finding them on the ground. The oxide spots won't amount to anything unless they corrode deeply, in which case you'll see verdis gris on the brass. It is highly unlikely you have that problem from your description. Ironically, a modest oxide layer actually protects cases from additional corrosion. This is why military brass is only cleaned but not polished after manufacturing and the neck annealing oxide stain is left in place.