Battery performance in cold weather is getting worse in cold weather when running for short periods of time. If you are running TCH for more then 2 hours battery becomes warmer and cold weather does not effect on the battery. Plus battery cooling system takes warm air from cabin which keeps battery warm even when the trunk is cold.
Concerning your question of outdoor storage of TCH - I think no one can tell you about it, because TCH is rather new model and no one knew how long the battery can last at those conditions. Rumors say it about 3 years, but I think about 8-10 years.