What if my doberman is alone for 6 hours?

I'm planning on getting a Doberman in the summer. I have done my research and it seems as if I had to choose between the Doby and the Shepherd, but the Doby gets the edge.

I go to school during the regular school year from 7-2. Would my doberman have a hard time doing nothing? I will walk it in the morning before school to get it tired and in the evening, each walk about 45 minutes. I will be really loyal and nice. All it takes from the Doby on his side is the patience.

Any experiences?