and some other dude posted this (I'm not copying/pasting the grrm livejournal links to the dates):
GRRM is completely and utterly incapable of predicting his own future writing progress. He has a tendency to always think he's just 'a few months' from completing a project, when in reality the end might be years and years away. Just look at the history of ADWD.
Famously, in 2005 he said ADWD would 'be along next year'.
Then...
June 2006: "Meanwhile ... I am still working on A DANCE WITH DRAGONS, and yes, I still hope to deliver it this fall, or by the end of the year at the latest"
October 2006: "I have half a dozen different projects on my plate, but the big one is A DANCE WITH DRAGONS, and I am going to be pushing hard on that in the weeks and months to come, in hopes of wrapping it up by the end of the year"
December 2007: "I do have some goals for 2008... the most urgent of those remains A DANCE WITH DRAGONS"
March 2008: "If I can deliver the book before the end of June, you'll see these in your favorite bookstore sometime this fall"
Feburary 2009: I am trying to finish the book by June. I think I can do that. If I do, A DANCE WITH DRAGONS will likely be published in September or October."
July 2009: "It is going pretty well actually, I am hoping to finish it by September or October that is my goal."
And so on. ADWD finally came out in July 2011. And even that was when the publisher basically tore the manuscript from his hands (because he would have needed 'another year or so' to write the battle of Meereen).
He never realised the book would be years away. At no point did he say "you know what, ASOIAF fans: ADWD needs a lot of work, so I need everyone to sit tight for a couple of years while I finish it up". Instead, he constantly thought he was just on the verge of finishing, while in reality being years and years from the end. Basically, GRRM has been doing this for >10 years. Time after time, he is completely incorrect about how fast his future writing speed will be.