Here is a thesis presented to the University of Waterloo in fulfillment of his requirement for the degree of Master of Applied Science in Chemical Engineering by John Catton.
Calendar Aging and Lifetimes of LiFePO4 Batteries and Considerations for Repurposing.
Thesis linkFor those that like the more technical info other than second hand info from folks that read it somewhere whether it's factual or not then repeat it like the gospel.
This is Lifepo4 chemistry not one of the other lithium chemistry types.
12v 500ah, 20 cells_ 4s5p (GBS LFMP battery system). 8 CTI 160 watt panels (1,280 watts)2s4p,Panels mounted flat. Magnum PT100 SCC, Magnum 3012 hybrid inverter, ME-ARC 50. Installed 4/2016 been on 24/7/365, daily 35-45% DOD 2,500+ partial cycles.