My longest render to date was over a week, on a quad core PC, I had to stop it before it finished since it obviously wasn't going to make the deadline by the end.

But it was an animation and it was my own fault it slowed up near the end, as objects with complex materials were getting closer to the camera.

In the end I changed the output to .bmp files rather than a single avi, and just stopped it when I couldn't wait any more and used what had been rendered rather than wait and fail to have anything.

Measure your mind's height
by the shade it casts.
Robert Browning (Paracelsus)

Fran's Freestuff

http://franontheedge.blogspot.com/

http://www.FranOnTheEdge.com