Shooting 4K at 30 or 24 fps will have no problem. You can shoot for hours or until the battery goes dead.
4K at 60 fps may run warm, especially when shooting in warm or hot weather.
4K at 120 fps will probably be limited to 15 or 20 minutes before a cooldown is required.
Shooting 8K downsampled to 4K gives great results, but will also be limited to 20 or 30 minutes before a cooldown is needed. In hot weather, the limit may be 10 minutes.
2 hours are needed for the camera to completely cool down.
The Canon R5 C has a cooling fan to address this issue.
Tom's Digital Photography Info / tom@mmto.org