This is probably why George R.R. Martin has not been able to finish the 'Winds of Winter'

Fans face an unprecedented wait for George R.R. Martin's "The Winds of Winter," now longer than the publication period of the first five "A Song of Ice and Fire" books. A growing number of viewpoint characters, ballooning from eight to thirty-one, is cited as a primary reason for the delay, creating immense narrative complexity.

Raccontata daeconomictimes.indiatimes.com