I am having similar thoughts. Thinking about a d800 for landscapes and long exposures. I think I need a second body to expand the functionality and to offer duplication for backup. I find it cumbersome when i am spending hours at a great landscape site and I have to wait on average between 5-10 mins between exposures and I dont have a second walk around body. I think the 5D3 is superior to the d800 in practical terms although the d800 is superior on paper and could have been a better camera had it not been for some quirks, bugs and quality issues. To have both canon and nikon gear I would have to have some duplication like maybe a few gp zooms and higher quality lenses in areas where the nikon shines - like with the wide zoom etc.