Re: One Lunar Day?
As Vulch said, it's all about thermal management. Lunar nights (because they are so long) are very cold. While the electronics themselves don't mind, most batteries can't survive such low temperatures, meaning that as the sun rises again there's no longer a power buffer available for things that take a lot of energy in a short burst (like transmitting data). While the craft might not be completely dead, effectively it is.
Due to the length of the night just adding more insulation isn't enough to keep things warm, you really need a heater. Spacecraft design is always a balancing act of vehicle weight versus the power available from the launch vehicle and decent stage. In this case they probably decided more instruments outweighed the benefit of extended mission time.