I say use as much time as needed; it should be at least as epic as this.
The final set of episodes will be at least 11 hours long, and the series finale will occupy three of those hours. However, there’s a chance that the series finale could expand even more. The “Battlestar” series finale will definitely expand on DVD. Regardless of the length of the finale that airs on Sci Fi next year, an even longer cut will be released on DVD.