I've got it mapped out another 5 to 10K words, then...well, I've purposely avoided thinking about the ending. I want it to be fresh, like a new start. I've prepared the story, the characters, the plot, and all that is required is resolution.
Of course, the ending is supremely important, after all it's what people will remember most when they finish reading.
This is total trust in my subconscious.
The reason I'm holding off is that once I've figured out plot, it loses some of it's freshness to me. Once I know what happens it's a little like coloring between the lines. It's almost preordained. There are always little surprises, but it's hard to completely change a plot once I've come up with one.
So...I have the book plotted up to 55K words. The last 15 or 20K words will probably be mostly action, which is relatively easy to write. (As always, when I say "easy" I don't mean easy to be good. If that makes any sense.) The final 10 or 15K words will come in the rewrite as I fill in the book with adequate description, telling detail, and clarifications.
But I want to leave the ending blank until I'm ready. By then, I'm hoping my subconscious will be excited to deliver. I intend to research the endings of all the various takeovers--Ruby Ridge, Waco, Bundy ranch, and Malheur and figure out a killer ending.