Have the deluxe edition pre-ordered (digital from psn store), just got a ps4-pro too. Good to go.
Curious about the 16 hour battle. FF 12 had that one very long boss/hunt battle, but by that time, nearly everything about combat was automated by gambits. I remember the Ultima weapons from 7, but they were fairly automated too with mimics and knights of the round table. You start, get hit once, and the counter proceeds an endless summon until weapon was dead.
Since FF 15 is active combat, I wonder how focused you have to be for that amount of time. If it is hard, you risk dying, which I suspect will cause more broken controllers than Dark Souls if it phases into the final stage at hour 14 and kills you due to poor timing/missed dodge of a oneshot ability. If it is trivial (tape down X key and go to bed), it is just a time sink.