The retrospective meetings are an integral part of the inspect and adapt process in Agile and Scrum. It should be held at the end of every sprint after the sprint review meeting. The team and ScrumMaster meet to discuss what went well and what to improve in the next sprint. The retrospective should be time-boxed and should result in a practical action plan for improvement.
RULE OF THUMB: How long should retrospective last? [reference]
A retrospective for a 30-day sprint should last about four hours. However, the retrospective should be tailored to the needs of the project and the experience of the team. For teams new to Agile, the sprint retrospective will take longer at first but will gradually take less time as they get used to the activity. Alternatively, as they start to realize the benefits of the retrospective, the time may actually increase because the team will be more engaged in subsequent retrospectives.
Did you review definition of READY? Don't forget to check more Agile Helpline Rules of Thumb here and don't let the following happen in your team....