Nietzsche was like a lot of those who are regarded as great thinkers; he was able to somehow get a lot of things right, without benefit of the additional information and techniques which make it easy for us now to recognize that they were right. Also like many of the great thinkers, he was overconfident and of course he also made mistakes. I think it is a defect in his work that he was not more systematic, as being more systematic makes it easier to test for conflicts and errors. Still, he was much more alert to problems than most; he was good at criticizing himself, which is surely an important trait in the effort to be less wrong. His views certainly changed over time as a result; he revises a lot of his opinions from Human, All To Human in Beyond Good and Evil, even though the latter was written within ten years of the former.