EC2 EBS Free Tier - Is Storage Reusable?
While I can't find it explicitly written anywhere, I do know that textbooks frequently reference that you can use the free tier to avoid costs, and that they frequently have you create and destroy instances between chapters.  So, I find it extremely hard to believe that you would get billed for deleting and creating new EBS volumes.

So, I believe that if you create a 30GB one, destroy it, and create another, you should be fine.  You should definitely make sure to remove the volumes and any related snapshots though just to be safe.

They definitely don't seem to explicitly confirm that though... e.g. in text like this:


  Notable offers for the first 12 months following your AWS account sign-up include some level of free usage for Amazon Elastic Compute Cloud (EC2), Amazon Elastic Block Store (EBS), Amazon S3, Amazon Relational Database Services (RDS), and many other useful services.


They use the free tier to get customers hooked.  They want you to like it and not be frustrated so you're more likely to use the real services and so that you may advocate them in your businesses.  So, by that logic, I similarly find it hard to believe they would "trick you" by billing you in this situation without making it more obvious.  That would be bad for sales.