I agree that it's always wise to have 2 bodies for any serious photography, having had 6D suffer humidity-related temporary shut-downs on more than one occasion. 4 minutes sounds about right for a long clip on a pro shoot, unless of course it involves interviews or something else that continues for a longer period. I guess that is what concerns the videographers that complain about the heat issue.HOT! Rajasthan, India in summers!! Also studios - but they were airconditioned. The longest clip was say 4 mins. I would turn off the camera between takes and we had at least a ten min gap between takes. Regular filming process. One hot afternoon I saw the heat warning and I quickly finished the shot and shut the camera. It was my production, my equipment, me directing and filming so I could adjust. If the filming was for someone else, I would not be able to turn off camera so often and believe overheating would certainly be an issue. I will say this: It is best to have two R5 bodies onset if a documentary-style shoot is on. Commercials/Videos provide enough cooldown time. Yet, even then two bodies would be better.