Is there a way you can resume renderings with cycles in AVI JPEG Format? Like if you wanted to stop your computer and give it a break and then start off the next time where you ended it? I don't know, it's just a question I've been asking my self a long time
I don't think so, so just render each frame separately and use them in an image sequence when rendering the movie. That way you can pause the rendering any time you wish, and simply change which frame your starting from when you begin again.
To do the rendering in different sessions, render as an image sequence first. Make sure you disable the Overwrite option on the render output, that way the frames that are already rendered will be unaffected, no need to change the start point.
Once you are finished rendering all of the frames of your scene compile the image sequence into a video format.