When moving from a plan-driven traditional milestone-based project management approach for developing products to an agile approach, there is a shift in focus from managing and owning the project to managing and owning the product. Teams are not started and stopped as each new project starts or stops, teams are longer-lived and allowed to learn and grow together.
They are encouraged to build and fly their own jets. Remember when you add a person to the team, or remove someone from a team, you begin a cycle anew of forming, storming, norming and performing. Psychologist Tuckman’s original report on this can be found here.
High performing teams won’t happen if they shift every few months onto new projects with new team members.
A caution here: if you’re moving from a project-driven way of developing products or services to a product-focused way of developing products, and you don’t have someone acting as the role of the product navigator, visionary, interacting both with the customer(s), business and the team, this shift will not occur.