Okay, so here's the whole (simple) story based on real-life experience...
Heading off to Australia for two months, I put my Karma in hibernation by disconnecting the Big Black Plug (BBP). I could have released the handbrake, chocked the wheels and stuck it in neutral, but decided to risk it (maybe for a longer time next time). After two months (Oct. 20th to Dec. 26th), I followed the advice of @PowerSource
and started the revival of the car by attaching my 12V booster battery to the car as advised in Karma's own Jump Start Video. Interestingly, when I did this, there were a lot of clicks and whirrs, which I did not expect. I then connected the BBP (when I would normally expect the clicks and whirrs, but there were none). I started the car up and reset the handbrake as per dashboard instructions. I left the car running for a few minutes and then disconnected my booster battery. The car continued to run normally.
After leaving the car running/idling for a few more minutes I turned the car off and connected my Trickle Charger. What I learned with the TC is that after hibernating for two months, the 12V battery was still at 80% SOC. I believe this is an original battery, so it's possible that age contributed to that 20% loss after two months, but for me it is good to know - it means that I could probably get away with five months of hibernation (assuming 50% loss) without too much worry.
Given the simplicity of this procedure, however, I won't be testing my hypothesis. I will always boost the 12V battery before reconnecting the BBP.
Thank you all for the help - interesting experiment!