When you are building a new product in your startup or company, you need to have a launch date or you have milestone dates that must be met. Your epics are done but since your team is usually new, no one knows the team velocity. Quite a conundrum.
This seems to conflict with standard Agile tools, but it does not conflict with Agile principles. Just add a dash of project management.
- Bring the team together and estimate the time for each Epic.
- Group the Epics into your milestones and calculate the dates.
- Put the milestones into a project schedule and determine the negative float.
- Themes are your friend. Examine the themes, epics and user stories and rank them.
- Apply lean startup techniques to validate each key hypothesis.
- Add and subtract stories.
- Get to work and start calculating velocity.
Remember this is a team project, but you need to be willing to ruthlessly drop stories and epics if they don't directly contribute to your core value proposition.