There are not hard rules around this, but it should be as low as possible. Most teams have less than a week between when one Sprints finishes and the other one starts, this allows for things such as Sprint Planning and Retrospectives to occur before the new Sprint starts.
Who in the project should give/assess the story points?
How to transform the hierarchical model of a company into Agile?
What about Project scope in Scrum? Who defines/make Project scope and how?
Product vision in scrum is a kind of “Project Mandate or idea”? If yes then what about Business case and Project charter in scrum?
Do I need to have all my users stories ready before starting a project?
What are the different methodologies in Agile?