I love SNW, but I think part of the earlier shows success is twentyfive-ish episodes per season. You got so completely random plots once the writers are out of the big ideas. Some of them are really bad, but some of them are pure gold. And all of them dig deeper into characters and relations than strictly necessary for the season plot.
It was probably not as fun for the writers and actors. I wouldnt want to demand they overwork themselves for my entertainment.