Please help me understand the 12 volt battery and traction battery

Generally the 12V battery will only be "damaged" if you leave an interior light on, overnight, for example. Some have forgotten that the overhead light switches have three positions, one side is "door" (open door turns on the lights), centre is off, and the other side is always on (for finding that money you dropped in the car ). This was on the GII. I -think- the GIII is smarter than that. I know Pearl S will turn on the lights if I'm just standing next to her with the FOB in my pocket, and I'm pretty sure if I leave a light on she will turn it off eventually, though I'd have to check that to be sure. Also, in the GII, you could turn off the car and the headlamps would stay on unless you opened the drivers door. Some would drain the battery by turning off the car but sitting in it waiting for someone, listening to music. Headlamps on, radio/CD/phone music playing. Again, I -think- the GIII is smarter than that, turning off the headlamps after some time automatically.

The cargo area light is often the culprit, as it's not obvious when it's on unless you are back there.

If you don't strain the 12V battery by fully discharging it a few times, it should last at least 5 years, like any "normal" car's 12V battery.
For example, Pearl's 12V battery is still the original, and Pearl is a 2007 Prius. I did add distilled water to it at year 3, but the battery is probably going to die this year (current owner has her parked for the winter with a "Battery Tender" keeping the 12V charged), because it's time.

Sulphate drops off the plates over time and builds up at the bottom, eventually shorting (resistively) a cell. This causes the other cells to overcharge as the system tries to recharge the bad one, and that quickly leads to battery failure.

 

There's also (unswitched) lights on both front doors, and in the front foot wells. I believe the footwell lights stay on even if the front doors are closed, but the hatch is open.

 

... and also battery drain roughly equivalent to a dome light left on if you leave a door open or only half-latched, even with all the interior lights switched off.

 

And that is because you can't turn off the front door lights. Well, you can, but you have to destroy them to do so.

 

No, I unplugged the wires on both those useless lights (without destroying anything!), and subsequently still ran down the battery (to 8.5 volts) by inadvertently leaving a door half-latched for about 60 hours. Upon recharging the battery, I measured about 0.68A drain from the battery with all interior lights off and a door open.
0.68A×12V=about 8 watts.
0.68A× 60hr=about 41 A-hr.