In my opinion, the show didn't jump the shark with the New York vs. New Jersey war, per se, but how they went about it. By that I mean, they set up everything perfectly at the end of Season 5. A regular 13 episode final season would have been perfect to follow that through to the end. But Chase and Co. took the money, putting $ over quality, and gave us a two-part final season with 9 additional episodes...resulting in a lot of down/wasted time. Then they speed things up way too fast towards the end.