Save yourself some trouble and break it up. In fact for rendering animations that are anything more than tests, you will want to render as seperate frames. If Carrara crashes or your computer, you just start rendering where the program crashed. Or if you need your computer, you can stop rendering and pick up later. After you have rendered all your frames you can use another program to assemble them all at once as a movie. You can also do it in Carrara, but you have to watch that Carrara doesnt oversample your previously rendered images. Besides, it is faster to use another program that supports image sequence import. Look for a program called Fast Movie Processor. It is an old program but it works great for taking rendered image sequences and making movies out of them. Finally, if you watch any films or anything on TV for that matter, you will notice numerous cuts employed. Since, you are going to have cuts anyway, it is better to storyboard your scene with the idea of different shots in mind at the start. Each unique shot can be a different rendering. This gives you more flexibility and will help you organise your ideas. BTW, when I say storyboard I dont mean the one in Carrara. Take some paper or a text document and outline or storyboard your animation. This helps tremendously, especially with lengthy animations.