For the most part, hybrid still/video cameras are limited to 30 minutes of continuous shooting, so that's the maximum clip length before recording stops and you have to restart. This is a deliberate limitation to avoid being considered from a taxation perspective as a pure video product. That being said, it's probably more important to think about how long the clip can be before your post-processing chore becomes unmanageable. I wouldn't want to be editing full thirty minute continuous clips. I would prefer to edit 3-5 minute long clips, knowing that for the most part, I'm not going to pull more than a minute of video from it and likely archiving or dumping the remainder.