I think experiences vary greatly based on company and domain. I work on a team supporting features for an app that is used by tens of thousands of people every day. Yet, what we plan to produce at the beginning of the quarter rarely matches what we actually produce. Example: my team spent months working to integrate our app with a new data gateway service. We were, I dunno, 75% of the way there when executives decided the data gateway should not be used (this months after they said this same gateway was the future of the company). So, I'm not pretending when I say sometimes, I don't know my destination. Sometimes I think I know my destination, only to find that both my course and the destination have changed.