Well I can tell you, it's taken me longer to read through A Feast for Crows then it did the other books in the series put together. I am just not as pumped to read it as I was the others, I'd say it's taken me nearly six months to read it, and I am only halfway through.
Some of that has to do with my fatigue too, but most times if I am into a book, fatigue won't slow me down as much. Just means I may only read one or two chapters.