Once I tried pressing the ISO button from time to time and the 50D can record raw video until overheat, which is about 82 min (in a cool environment, with a single fully charged Canon battery). I believe it is because of the power saving in the Canon menu. The longest duration we are allowed to set is 30min. So as I press ISO button during RAW video recording it would reset the counter.
By the way, I found that showing live histogram would make the 50D crash after about 6 min. But if I use global draw and activate the zebra and focus peaking, it can safely allow us to take video up to card full.
I am testing this since I wanted to use RAW video in an upcoming wedding proposal job. I figured I can get full sensor, 2.39:1 output (1568X656) for about 25 min. from a 64GB card. So I am wondering if I can get continous 50 min. from a 128GB card and from my testing it seems ok. (Can go pass 30min, and overheat and battery life doesn't matter at least for the first 80min.)
Probably not too many people would be interested in RAW video "marathon" but if as least it is possible for now.