Only way you can go wrong with an Epson printer & ink is to use cheap paper or to not use it often enough. I've had my Pro 4000 sit over a month and then had to use extensive cleaning cycles.
It is most important (as with any camera) to get a very sharp image. But, the D800's higher resolution shows user error mo beta. I have cropped and recropped and then printed 17x22 with stunning results.
My guess is that 64" roll paper is not too wide for a D8000 print.