Given that the Plutonium power core is putting off 2000 watts of heat in order to generate 125 watts electricity, I find it surprising that they don't have enough heat to keep wet-lubricants heated sufficiently. But - that's an awfully big Rover, and it does get pretty cold on Mars...
2000 watts at 14 years in kilowatt hour - 245,000 kilowatt hours.
Remember, it's got a 14 year lifetime because the half-life of Pu-241 is 14.1 years. At the end of that time, half of its mass will be gone, and it'll be producing half as much heat. It won't produce a steady 2KW for 14 years and then bing, go out like a lightbulb. Power produced will slowly fall over time.
You mean, half of the plutonium mass will be gone. It will be almost completely be replaced by other elements. Though I don't know how much energy they give off in radiation, or whether they are stable.
http://msl-scicorner.jpl.nasa.gov/Instruments/Mastcam/
James Cameron lobbied to make zoom lenes for the cameras so they could be set at the same zoom level to create stereo pairs for 3D images.
JPL had "problems designing the lens without using wet lubricants which would require battery-sapping heating"
Difficult trade-offs must have been made everywhere - who knows where that extra battery power went that the zoom lens gave up.