Sorry, that's not what DSLRs are made for.
Every dumb camcorder will do just fine.
If you insist doing so you have to use an external power supply (Canon AKG-E6 or else).
H.264 will interrupt (with some noise) after 29:59:59 continuous recording, shutter will close, mirror will come down and ML will restart recording. You will loose about 0.5 seconds (as far as I can tell). Data rate is about 6 MByte/s in 1080p -> 2 hours = 7200 seconds -> about 44 GByte.
Recording in RAW/MLV will do seamless but cause serious data streams. Do calculation:
7200 * Vertical resolution * horizontal resolution * 14 * frame rate / 8 = Bytes
Or other way round: Biggest card available has about 238 GByte. Will give you about 889x500 resolution.
And in both modes cam will heat up and - if limit is reached - will just stop recording. If it hits limit or not is unpredictable from here. Depends on your environment.