Probably you wait for around 3-5 minutes if you have the lens detached from the R5. I guess a wide lens mount throat of R5 will assist in equalising camera internal temp with the ambient fast.. the sensor is covered by curtains anyway.I honestly thought 8k Raw would be limited to 5 minute bursts when I first heard about the specifications. I'm suprised it can do 20 minutes at any temperature. It's just a shame it takes so long to cool down. If you could wait 10 minutes and then record for another 20, it wouldn't be an issue at all IMO.