I would like an option to render by doing one pass per frame and moving on,and when they reach the end of the video run the next set of passes. I do not know how this would work performance/software-wise, but I have gotten used to setting the allowed pass limit higher than I need, letting it render until it looks "done", saving, and canceling the render. This is great because it removes the need for pre-renders to figure out how many passes I want. I however figure that this is probably not feasible, and it is just an idea I am throwing out there.