I don't know that I've spent more than 4 consecutive hours in the Animal Kingdom. When I was there last, in 2008, I had a nagging feeling that I was missing something in the park. As it turns out, I wasn't missing anything, there just wasn't much there to begin with.
Avatar Land is the equivalent of jumping the shark. If they build a land based on a flash in the pan movie nobody has seen twice, I will sell my Disney stock.