The best length is around a month before deleting any video evidence (screenshots you can delete immediately since we store screenshots online). We ask you keep video evidence for a decent length of time is because the people who were banned for it need to be able to see the evidence and appeal. So say they claim it was a false ban or the username was slightly incorrect so the wrong person was banned, and the evidence was deleted, that person will likely just be unbanned since we don’t have the evidence to confirm or prove otherwise