8K wow….4k120fps wow! On paper this EOS-R5 is a super camera. But how does this translate in the reality? Canon upfront disclosed that there are some serious limitations. For example you can only shoot 8K video for 20minutes at room temperature. Which means that if you shoot outside under direct sunshine or in a hot day you might not be able to shoot 8K at all. Also the cooling time is quite long and will only allow you to shoot even shorter videos after (see tab on top).
Max Yuryev explained it well:
This is not to downplay Canon merits. But it should be clear to everyone that if you wanna do some more “serious” video work this camera might NOT be for you!