I don't have much experience shooting in burst modes extensively. But 45-50mb files multiplied by 12 to 20 FPS in short order for hours, we're talking between 500mb to 1gb A SECOND! That's a lot of data to write. And that isn't even taking into consideration DPRAW or writing dual files to dual cards.I don't know what this camera is fully capable of, but 'a few thousand bursts'- (we're talking hundreds of gigs), no, I'm not surprised that it would overheat doing that in any environment.
1. who shoots for hours at 12FPS? typically you would go with shorter bursts of 1-2, max 3 at a time..
2. DPRAW - is not your standard option.. not what you use for every single shot.
3. writing to dual cards - is not an issue. and never have been.
4. 45MB large files is not something extraordinary or new for Canon. : 5Ds, 5dsR, Sony : A7R3, A7R4
+++ no, I'm not surprised that it would overheat doing that in any environment.
A.M.: Understandable.. because of this: "... I don't have much experience shooting in burst modes extensively...."
in reality, though, this is a requirement for indoor / outdoor sports and many other applications.
You cannot afford having a cam shutting down on you in a professional setting.. I hope that overheating of R5 while taking still frames was an isolated occurrence rather than a trend.