You can make backups of the data absolutely. There's a whole industry selling cloud-to-cloud backup solutions.

Some examples: https://www.ownbackup.com/ https://www.backupify.com/ https://www.cloudally.com/

Edit: to clarify I would say if the data is important to you, then “the ability to back up the data” should be a requirement when selecting saas. See my other comment in this thread on ms planner.