In situations like this, small changes can make a very big difference. For one, you absolutely need to cover the viewfinder when taking long exposures, even if the light coming from behind you seems small or non-existent. Remember, it's additive, so even the smallest amount of light over time will have an impact. Secondly, LR noise reduction is nice but is far from state of the art. For times like this with extremely long exposures, you need something a little stronger than LR. I use Nik's Dfine and believe it is probably the best product on the market for long exposure noise.
And I do remember your post and though I'm not an authorized Nikon repair technician, I do not believe you have hot pixels (at least not the kind of hot pixels I think of when I hear the words "hot pixel"). But if you are convinced you do have a hot pixel issue, send it to Nikon asap. But before you go dropping a large chunk of cash on a new camera, I would revisit your long exposure technique and see if these small changes can't make enough of a difference to obviate your need for a new camera body.