A photographer I know warned me against recording too long with my 5D Mark III and also 5D Mark II because the sensor would overheat and become damaged. I had heard rumors of this but nothing confirmed.
Another thread attempted to tackle the question (http://forums.creativecow.net/thread/325/1420) but I am not sure it was completely resolved.
If anybody has the answer or know where to get that info?
Using it under normal circumstances as per the manual should have no impact on your sensor. The best thing I recommend is purchasing fast CF cards so that you don't stress the buffer internally. The more the buffer works, the warmer the camera gets. I use Sandisk Extreme Pro cards in all my cameras and have not had any problems (7D, 5DIII, Canon C300).
I've been shooting DSLR video/stills for 4 years and have had no issues with the sensor on my DSLRs.
Under normal usage conditions, you should have no problems with damaging the sensor.
Given that you don't try to capture video for extended periods of time in extreme temperatures (greater than Canon designates as safe in your manual) and that you use Class 10 or equivalent SD/CF cards, you shouldn't run into sensor damage.
Should you run into sensor problems, Canon should warranty your device because the damage is most likely inherent of a manufacturer defect.
Rochester Institute of Technology
BS Digital Cinema/Motion Picture Science 2015