The longest render I ever did/designed was for a client, we used bryce lightning and 4 computers to render it and it took 2 1/2 months. Granted it was an animation in HD format heheh. As far as your other question it seems like we had tried that before during the testing cycle and it would either crash bryce or the render would stall etc etc, I can't remember now for sure, but I think it kills bryce when you try to view it during the rendering cycle.

Do atleast one thing a day that scares the hell outta ya!!