My 2011 C-Zero has about 90% left (assuming it had 16 kWh usable to begin with - it would now seem to have 14.5 kWh - 13 kWh to 10%). That's about 2% per year. I the first three years when I didn't have it yet, it only gained less than 10.000 km to it's odometer though. It has spent it's whole live in cold Finland. I've accidentally once tried to charge it while frozen, when CaniOn was reporting wrong temperatures. I don't know if the previous owners (including Santa Claus) have done it. Hopefully not and based on battery status I think they haven't.
kWsaki.com / EVs: Nissan Leaf 2012, Citroën Xsara 1997 (conv. 81V & 8" Series DC) and Kawasaki GPX750R 1987 (conv. 87V & ME1003 PMDC) / Used to have a Citroën C-Zero 2011