Battery temperature management seems to be a key limiting factor.
At least a few years ago, and likely still, the reasons and conditions under which the barrier layers in the battery degrade were not super well understood. Heat seems to be a key contributing factor and charging a battery quickly warms up the battery and I suppose not fully evenly within a cell. Not knowing the complete extent of this makes the early LEAF's lack of actively cooled battery a reasonable choice. Before that, the batteries of earliest Prius cars held up way longer than expected.
Like with a phone: heat and cold is not super awesome for the battery. It seems heat is especially bad for longevity.
I'm also waiting for this to move some 500 repositories from GitHub to a realistic federated alternative. I follow up from a distance but don't see much movement on ForgeFed for ForgeJo. Did I miss something?