Having been through multiple month long planning "phases", that were eventually shown to be wildly inaccurate I disagree. This is exactly what we used to do in

Having been through multiple month long planning "phases", that were eventually shown to be wildly inaccurate I disagree. This is exactly what we used to do in the waterfall days. It didn't work. The only way that's been compatible with me is to build something really small but valuable. So small that its hard to be disastrously wrong. Once you've released that value, build upon it. Stakeholders tend be much happier as they at least have something they can use really early on.