To be honest, it does not take a taon to produce a film and edit it. This is Summit's plan of trying to gatas the Twilight Saga of what it's worth. However, this isn't the best plan, considering, the momentum of the series is slowing down. I mean, look at the Twilight series spot now. All the fansites. Hardly any news, therefore, fans become uninterested until things pick up again.
So in answer to your question, there isn't rally a good reason why they are releasing part 2 a taon later. Splitting the movie adaption into two pelikula might serve the story justice (we'll see), but releasing them a taon apart is unwise.
The book was too long to make into one movie...they would have had to cut most of the story out....two movies...more of the story and madami money for Summitt ....lol
Its there way of making madami money, they are taking advantage of the movies because they are soo popular summit know people are going to pay to see it :)
I think they decided on doing them a taon apart instead of 6 months because there are supposed to be a bunch of blockbusters susunod summer. I'm not sure exactly what, but that was what the official release said.