I have an i-MiEV since april 2011. I'm from Portugal. The worst enemy of electric cars is the high temperatures, and the Nissan Leaf from Arizona showed that fast. My country is not so hot, but have high temperatures (more then 30º C) often in summer.
Most users with 2011 and 2012 will not see any difference. They will do now the same mileage (or very little difference) that they did two or three years ago. But that doesn't mean 0 degradation. That degradation maybe only can be found at very low SoC, and most of us avoid to take the car bellow 20% SoC.
In mine, there is clearly a difference between 2011 and 2014. Not easy to get the correct number, but I fill I lost between 10 to 15% of original capacity.
In Finland, because the high temperatures are not a problem, lost of capacity will not exceed 1 to 2%, I think.
If you want to know more of what an i-MiEV can do, you can watch some of my videos:https://www.youtube.com/channel/UCtO0sV ... a37X3XsNbw
Riding an i-Miev since 4/2011 in Portugal, 100.000 kms.