I would say when it comes to how often you want to have ad breaks, youtube content creators seem to be getting better at it! I have seen content creators make sure their ad breaks come exactly at moment which are in-line with their content such that it does not disrupt the flow of the content itself. It is definitely important to work it into your content properly and not simply drop ad breaks at random and too often as it can definitely irritate a potential long-term suscriber. You definitely don't want that.