Ok so I tired running 2 heroes. 3 packs cav 1 pack archers, avg kill speed 12 sec for 3 hours. Result is around 1.5 mil normals, which is insane imo. I have not even opened and candy canes.
The average I'm getting is 1k of each normal per box encounter. So by the time you do 500 big present boxes you should have 1.5 mil normals.