I would check with CS about that. It could just be that the book was withdrawn by the publisher, which would be unrelated to DL times, or some other issue. To limit DLing to 6 times would totally negate the concept of a Cloud. Hell, some of the folks who bought Paperwhites had nearly that many of them sent trying to get a good one. They would have maxed out on DLs in a hurry. And others have had at least 6 factory resets over the many kindles they have owned.