I think the best way to avoid an inaccurate estimation is to actually have members on the team that have done similar tasks before, you wouldn’t want to take the opinion of an inexperienced person. This goes to show how each phase of project management is built off of the previous phase. Within the planning phase, team selection impacts how the well the WBS will be composed and how well the critical task durations will be estimated. I know it sounds bland, but the best way to get the most accurate timeline for a task is to ask the individual who is experienced in the task, and will be the one responsible for its completion. Now in my opinion I think it is better to over estimate the time it takes rather than underestimate, because underestimation will lead to delays and can ruin the planning that went into later stages. The only real downside to overestimation is for example, a case where multiple project teams have to share a piece of critical equipment and your team scheduled their usage for 2 weeks from today because you had some project slack, but you’ve finished early and have nothing to do because you need that piece of equipment to proceed into the next stages. This looks bad on your team and is especially why expert opinions should be surveyed prior to scheduling for a critical task.