The sprint's purpose is to create the cadence or frequency of all the scrum events. Sprints will need to be long enough to ensure rapid feedback from customers and a continuous cycle of releases. Sprints need to be long enough for the team to achieve their goals for the sprint. Reviewing the development process and typical user stories are also essential inputs into the decision. Sprints are typically 2-weeks but could take up to 4-weeks. Check your velocity. If your velocity shows you are completing more user stories with high quality in a single sprint, then the sprint length is set correctly.
Can the development team produce a stable product for release within the sprint?
Large ERP, SaaS, and highly integrated complex systems make shorter sprints difficult due to the number of teams involved in adding new functionality or a change. A longer sprint gives teams more duration to coordinate with each other and finish work consistently for demo and review.
Is the product highly regulated?
Products that require government regulator approvals or significant oversight by external bodies (auditors) need longer sprints to allow time for approvals.
Is the right level of quality achieved during the sprint?
If poor quality is a common occurrence, additional development and testing time can improve the quality before demos and releases into production.
Is the majority of the product development or configuration outsourced?
Your sprint timeline and duration needs to align with the sprint cycle of the external product development teams.