The solution we have arrived at is based on several elements. First of all, not to say "we have X weeks, what can we do", but "we want to do this, how long does it take?". Then, to have mandatory design reviews along the way to avoid backtracking that breaks the momentum and delays the entire roadmap. Then, to make sure that design and PM have enough time by guaranteeing that they have at least 1 project ahead of the techs. And finally, that the discovery of each project is done as a team (tech+PM+designer) to guarantee the same level of information and be able to align on a solution early in the process.