We know what damages batteries, we know some of the chemical processes that degrade the ability of the anode and cathode to store ions over time and we know the things you shouldn’t do and those that you should.
Dahn, (who is also a technical advisor to Tesla) and his team helped develop the automotive lithium-ion cell and some of the materials they developed are used in automotive drive batteries today, as are their mathematical models and algorithms which manufacturers use to validate their battery data.
In the absence of hard data, meanwhile, it might be useful if the industry could get on and agree a universal battery-state-of-health document.