The number of people who might become angry because perceived lack-of-delivery of the book is much much higher for a TV show than for a book series.
So basically the same process Elmore Leonard uses and the late Charles Willeford used. The advantage Leonard and Willeford had - no, make that advantages - is that A: their chosen genre does not favour the sequence of book chunks model of writing and so each of their individual book had to go somewhere, rather than hoping all the plot threads would be dealt with in a future book, and B: the word count limit for mysteries seems to be very roughly 100,000 words, meaning there wasn't too much room to screw around in.
However, with additional season pickups likely considering [Game of Thrones]'s success, Martin is attempting to buckle down and finish his novels before HBO catches up.
[snip]
"Sometimes I make the decisions wrongly. My process as a writer is not one of thoroughly outlining ahead of time, which can result in my muse leading me down blind alleys and dead ends. … So then I have to double back and rewrite and so forth. It's almost a subconscious thing -- when it's right, it feels right, and when it doesn't feel right, I keep niggling at it until it does."
So basically the same process Elmore Leonard uses and the late Charles Willeford used. The advantage Leonard and Willeford had - no, make that advantages - is that A: their chosen genre does not favour the sequence of book chunks model of writing and so each of their individual book had to go somewhere, rather than hoping all the plot threads would be dealt with in a future book, and B: the word count limit for mysteries seems to be very roughly 100,000 words, meaning there wasn't too much room to screw around in.