Fluid UI automatically saves your work both locally and online every few minutes as well as every time you click the preview button - there is no need to specifically save or manage projects.
The only way your data will be deleted is if you ask us to delete it. We store data for inactive accounts for up to a year. After a year of an account being inactive you will receive an email warning you that your account is going to be deleted. If the account is active it will not be deleted ever.