A very common mistake is to assume that once your team is delivering features then your work is done. Teams are never in finished or in a constant state but rather something living and ever-changing.
Many events can cause a change in the team dynamics, productivity or mood:
There are frameworks to help you understand where your team currently is and how to help them move towards becoming healthy and productive team.
To set your team up for succes it’s important to be aware of the fact that Team changes require changes in expectations as well.
Hogan, Lara; Resilient Management Larson, Will; An Elegant Puzzle: Systems of Engineering