When your customer discovers what they really want in their project, ask them how they would like to handle it. You can push out the release date or add more resources (which is like saying we are going to need more money), or you can drop some of the less important stories from the to-do list (preferred).
Don’t get emotional when you have this conversation. It is not your call to make. You are simply communicating.
Your responsibility is to:
- make them aware of the impact of their decisions and
- give them the information they need to make an informed decision.
If your client really wants it all, create a nice-to-have list and tell them that if there is time at the end of the project, these are the first stories you will do.
But make it clear, the nice-to-haves are currently off the table and are not going to be part of the core plan.