These are false allegations.
7 hour CVR? Please.
I was involved in an incident in the '80's where they wanted to know how an approach to the incident airport went the prior day, with the same crew. They were able to get thirty hours of very clear voice off the thirty minute tape. When it's recorded, it is done over the last recording, not erasing it. It was costly, but I was very impressed with the quality, and this was back in the '80's.