This is what I know about 8k video recording. I use it frequently on my n20u. For 1 just a 1minute video uses about 1gigabyte of memory. Thats huge amount of data for 1minute of service. Next thing about he 8k recording is it will only load to internal memory while recording. That tripped me out when I was looking for the best memory card I could find. Fone stills records to internal memory. You can only record 4k 30and below if I remember correctly, directly to sdcard.
Next my n20u gets real warm with 8k video recording for extended periods.
Heat kills proessors and batteries. So anything that produces heat above ambient temperatures that you the human can feel in fingertips is not good for any sensitive electrical equipment. All you need is a thousandth of a millimeter gap and it breaks a circuit.