"And what is the major power draw that leads to such a short battery life? The heater to keep the electronics warm?"

Yes, it's in the other post:

    "It is very unlikely right now. We have 1.5 hours [of
    sunlight] at less than 1 watt, and 20 minutes of 3 or 4
    watts. The lander needs 5 watts to boot….In order to charge
    the secondary battery, we have to heat it to 0 degrees
    Celsius. We need about 50-60 watt-hours a day in order to
    reach 0 degrees and still have daylight left to charge the
    battery."

http://elakdawalla.tumblr.com/post/102615327170/philae-updat...