Should work. I record HD 1080 Video at 30fps for up to 80 minutes on Sunday Mornings. Never had my D800 overheat but have to restart the Video every 20 minutes. There is and external HDMI recorder (Ninja 2) that allows you to go at least one hour continuously. I think you would have to attach an external power source or battery pack to the D800 to record more than 1.5 hours
Check the Nikonians Video Forum for more information.