Well, statistically, heat and
Well, statistically, heat and aging are the main cause of prius battery killer. 2nd. And 3rd gen Prius use same battery cells. They last about 10 years inn hot climate, and longer in milder and cold climate, 15 years historically. 4th gen battery is better and have 15 y warranty in UK/IRELAND since its always rain and never gets too hot or cold there. So, the best way is put it in garage when parking. Failure rate in Florida, Texas, Arizona, Nevada, Louisiana, Mississippi are always much higher than Minnesota, Ohio, Wisconsin, or Oregon.