Which battery does it use? If it's an en-el15 and battery life is anything like my d7100 or d7000 than it should easily be good for all day. My friends d800 last all day with some life left to spare. I've only just picked up a spare battery and only due to a planned two night trip to skomer island where it's not possible to charge a battery. I would try your new camera first before deciding if you need a spare battery.