There are two lifespans. The shelf life and the number of charge cycles (less of a span perhaps) where you charge to 100% and discharge to near 0. If you keep your charge/discharge to 80/20 then your battery life is limited primarily by the shelf life. eg. keep your Nissan Leaf in the 20-80% state of charge range and it will probably last 20 years, DC fast charge it every time to 100% you'll probably only get 2000 cycles (5-7 years) out of it.