Why did the Jehovah's Witnesses change their blood doctrine so many times?

So you expect people to believe you because you pose a list? Very clever. We never say that we are infallible, the Bible is infallible. We never say that we are wrong but the Bible is never wrong. That is why we see fit to make adjustments in our understanding when Jehovah God mercifully helps us to discern where we need to correct our understanding. Even some of Jehovah's Witnesses will not survive the end. We are proud of our beliefs and our God Jehovah. There is no one in heaven or on earth that will change our appreciation for Jehovah's earthly congregation of Witnesses today. :)