Motorola V551 / V330 / V547 / V555 / V557

I have a question i have this phone and thought it strange that every time u record video it does it in different lenghths. What i mean by this is if i make a video that sometimes its 6 secods sometimes four seconds. When i make a video with the maximum lengnth i had one video that was a over a minute and some 40 seconds. I guess my question is there a way to regulate how long the movie clips are? 🙂