I haven't used this camera but know people that have. The 2/4/8 second shooting is called "Video Snapshot" which is an optional in-camera edit feature. I'm sure you can shoot until the card is full.
***With the Video Snapshot feature, the EOS Rebel T3i DSLR will capture short video clips (of 2, 4 or 8 seconds) then combine them automatically into one video file as a snapshot or highlights "album." ***