The shutter count has been the only indicator of usage/lifespan for second hand cameras to date. Video usage hasn't been an issue. Semiconductor lifespan decreases when run over their rated maximum operating temperatures. Canon clearly designs their SW to ensure long lifespan but these hacks can override this. It is probably unlikely to occur within the normal 1 year Canon warranty period unless they are doing crazy stuff but 5x more likely given the Canon Australia 5 year warranty.That seems unlikely. More likely either failed or operational. And >95% likely aren't shooting 8k to overheat on a regular basis. I have yet to shoot a single frame of video.
I will be trying some 4k120 tomorrow for some underwater video for the first time