Duration will of course depend on how much you want to achieve.
If you only want to work with ideation, a day will be enough. If you also want to work on concept development, you should at least plan for 24 hours, preferably 48 hours.
If you want participants to start working on a business plan as well, you should plan for a week.
To do-list regarding duration
- Agree on goal (how much do you want to achieve).
- Arrange duration according to resources.
- Arrange time schedule.
- Arrange that the time period fits into the schedules of the organisation.