I've had this "not finishing" problem in P5 on lots of things I've rendered hi-res for prints. Reducing bucket size seems to help a lot. Another thing to try is to reduce the geometric complexity of the scene. In some scenes, I found that I could safely remove objects from the left side and get a full render of the right side, and then vice versa. Then I would patch them together in photoshop. The real thing to watch out for is shadows crossing from one area to another that depend on all the geometry being there. Another one is to wait for the large render to freeze up, cancel the render, and then save the partial render result to a file. Afterwards (or for me, typically before), render a copy at half resolution. Then you can use the lower res to fill in the broken areas of the higher res image. Between those two techniques, I can usually get a high resolution image, but sometimes, it has taken as many as four or five images to patch the whole thing together. I've been told, but have not verified, that P6 lets you render rectangular sections of your scene. If so, you should just be able to patch it together with enough care. (For reference, some of these images were 3600 by 5400 and rendered on a Pentium 4 w/ 4GB of RAM.)