This is a tough one, but really the only bias is if suddenly one of your videos blows up overnight and gets a ton of views - this could skew the data and make it tough to make an accurate call. But if you want to be super safe, delay the test 2-3 days after publish, and as long as you don’t suddenly go viral, the test will be accurate. And if you do go viral, who cares about the test 😀