I watched a video a while back about Electric Vehicle batteries. It said that the EV lithium batteries live longest when run from ~90% down to about 50%. Deep draw and 100% charges reduce life - they said. I don't know... I try to do that with my iPhone.

I do like the fact that Lithium can be stored long term without losing charge. As JK said, disconnecting them from the vehicle is wise due to a parasitic draw of computers and such. Sitting discharged kills typical auto batteries very quickly...

Speaking of long-term storage, I've found that AGM (Absorbed Glass Mat) batteries keep their charge over winter as well as Lithium. The ATV/motorcycle industry went to AGM batteries quite a while ago. It's what I buy when replacing a battery in my motorcycle. These are maintenance-free once past the initial fill. What is an AGM battery? Go Here.