Isadora will automatically deactivate when your rental period ends, and will revert to Demonstration Mode.
Previously created Isadora files are not affected in any way. They will still be open and run while Isadora is in Demonstration Mode, but you will not be able to save any changes to new or existing projects.
If you later rent Isadora again, or purchase an Isadora Perpetual or Subscription License, you can simply use your new license activation information and follow the steps in our article on how to activate an Isadora license.