With regard to RJ, I think it is hardly a certainty that he lengthened the series for commercial reasons when his own poor planning and writing style are equally probable and sufficient reasons for the ballooning of the series. None of us knows for sure. In any case, in RJ's defense he was trying to give his fans what they wanted even while he was fighting for his life. He even allowed for another author to finish his work, a decision that would have been quite personally painful.

GRRM just quit trying quite a while ago. Its been 10 years since the last book. He could have finished book 6 by now but he just doesn't care. He has been giving his fans a morbidly obese middle finger years. He has let his readers down much more than RJ IMO.