720p records at 59.98fps. You need to reduce the image size and/or use FPR override to slow down the frame rate. Look a the bottom of the screen when adjusting the image size. Green means it should record continuously until the card fills up but if it is yellow the data rate is probably too high and you'll get the frame skipped warning and recording will stop.
By the way, you will get better quality if you set the Canon menu at 1080p mode. Note that the frame size should still be no larger than 1280x720 which causes some confusion over the difference between mv1080 mode and mv720 mode. mv1080 skips three lines horizontally and vertically (3x3) and records natively at 24, 25 or 30 depending on your Canon menu settings while mv720 skips three lines horizontally and five lines vertically (3x5) and records natively at 50 or 59.98 depending on whether your camera is setup as PAL or NTSC.
