And to add a little additional to Rick's answer (and he is absolutely correct):
The camera manufacturers really don't design DSLR and mirrorless bodies for continuous camcorder service. Far more heat is generated with constant operation of the sensor, A/D conversion, storage, and overall control functions of the device in video service than is found with still image use. Dedicated camcorders have cooling systems, usually forced air, to deal with this while what are primarily still cameras are biased more towards weather resistance than heat rejection. Canon's EOS 1DX family use a heat pipe design to manage where heat builds up which is far more robust than their pro-sumer and consumer bodies but in high ambient temperature operation a 1DX can also go into protect mode in video service. Long before over-temp limit modes are hit, increased aging of components is occurring in these bodies which is a concern if you plan to keep your camera for a long period of time while using it heavily for video service.
Or the short answer is, for extensive video operation you are better off with one of Canon's dedicated camcorders or if you need extensive lens versatility the EOS cinema line. The DSLR and mirrorless bodies are fine for occasional video use that preferably doesn't come near the "VAT tax" record time limit but they are primarily still image product with varying levels of video capability. I use a XF-400 for sports video and it does a great job for as many hours as I want to shoot even in the summer but it also has a fan that I leave set to continuous duty to control heat buildup and I am careful that it doesn't see even the light rain exposure that my 1DX series cameras and L series glass often sees. The XF-400 also has the ability to capture stills but certainly not at the level of my 1DX series cameras. Each is very good at its primary task.
Rodger
EOS 1DX M3, 1DX M2, 1DX, 5DS R, M6 Mark II, 1D M2, EOS 650 (film), many lenses, XF400 video
