I am 10,000 miles into my Energi Titanium and love it! As someone who has always kept cars a very long time (7-10 years average) how long can I expect to get out of the EV/Hybrid Battery Pack? Will it like many batteries lose its efficiency over time and if so, how much? And although it will likely cost different than it does now, what is the realistic cost of this replacement? That's assuming it can even be done cost efficiently.