The value should be demonstrated at the end of each iteration to engage stakeholders and receive feedback on the development progress. This practice aligns with the agile methodology, where iterative development and frequent assessment are key components. Demonstrating incremental value at the end of each iteration allows for adjustments to be made based on stakeholder feedback, ensuring that the product evolves in a manner that meets their needs and expectations.
References: Practice: Iteration Demonstration and Review - Project Management Institute1.