I have been keeping records for all of my charging, including SoC at the beginning and end of each charge and the kWh used. So I plotted the kWh / change in SoC as a function of the odometer miles. I am not sure if there is a direct relationship between the [kWh/ delta SoC] and the battery capacity, particularly if the buffers undergo any change over the life of the battery. But if there is a direct correlation, then a 1/3 drop in that value will happen around 73K miles according to this linear relation. But I think the degradation is not linear, and the rate of loss tapers off after the first year or so according to plots published by Honda for other EVs. I expect the battery will probably show less than 1/3 loss in capacity over 10 years or 100k miles.