How does the Nikon D5 handle? Pretty much like any other pro Nikon camera that's preceded it. My two bodies are daily-drivers and do a lot of mileage over harsh terrain in all weathers. They're robust and great for covering protest & civil unrest. While jostling amongst Black Lives Matter protesters in Bristol they took a hammering and still managed to capture that key moment when Colston was dumped in the water.
Is the Nikon D4S still a good camera? Yes, certainly and absolutely! Mine has had as much punishment you can give a camera, including a few embeds in Afghanistan where I was capturing images like this 105mm light gun battery firing offensive volleys during night operations. This camera is still a daily workhorse and, although a little battle-scarred, still fires every time to produce double-page picture quality.
How old is the Nikon D4? Well, it came out in 2012 and although mine isn't an earlier model, it is knocking on a bit and lacks some under-the-bonnet image processing refinement of its successor. I still use it on a daily basis, especially on big assignments when I can shoot fast, by not swapping-out lenses. It also gets the brunt of any dirty work, like this image I shot at Weston Beach Race - it got covered in wet sand!