I think those are fine concerns. One thing that Alex and Christopher has said before is that 1) Covecube isn't in any danger of shutting down any time soon and 2) if it would, they would release a tool to convert the chunks on your cloud storage back to native files. So as long as you had access to retrieve the individual chunks from your storage, you'd be able to convert it. But, ultimately, there aren't any guarantees in life. It's just a risk we take by relying on cloud storage solutions.