Actually the battery life on
Actually the battery life on my 3 Volts increased slightly over time. However I have seen degrading batteries with friend's Leafs, but they were air cooled. One nice part of PHEVs as used cars is that for many of them the gas engine was barely used, and mostly just for long trips. (I averaged 171MPG in one of my Volts) So 4 years driving in a PHEV is equivalent to the wear of just one year of a conventional gas engined car (for those of us who drove mostly in EV mode). And the regenerative braking meant that the brakes were nearly new too after thousands of miles driven.