Yes, I also don't think they would focus much on the idle power saving, because very few cameras spend any significant time in that mode.
I would really like to use a Canon camera with chdk for a long timelapse (2-3 months), but except for a car battery, there is little chance I could waste almost 0.4W each hour.
I hacked a cheap, broken Samsung camera, attached a PIC controller with a phototransistor and potentiometer (the phototransistor is to prevent it from turning the camera on at night, and the potentiometer to set the delay), then attached a solar panel, and it took photos for almost 2 months, until the 2gb card got full (this camera won't support HCSD). But a Canon camera with chdk would be much nicer, because I can adjust the focus, do long exposure stuff so that I can take pictures at night too, and many other cool things. I wish I'd knew where all that power goes :/