Well, the 4/2013+ build months having probably better packs has been mentioned a countless number of times here.
I can't speak to all other places though.
I haven't had a chance to read this whole thread but +1 on the advice of 120 volt outlet at work. If one charges all day on that, that'll really improve the useful life of this car for this commute.
I had a April 2013 SV, The battery dropped pretty bad, almost like the Pre March batteries. However it did not look the 9th bar before the warranty expired. Range has gotten pretty bad and was starting to become an issue till the car got hit and totaled. It almost feels like the car had 1/2 the batteries with old chemistry and 1/2 with new.
The cars I drive on a regular basis.
2015 Smart EQ
2014 Spark EV
2011 Leaf SL, bought as 4 bar looser!
2013 Tesla S85
2013 Tesla P85
2015 Fusion Energi, Gas guzzler!
2016 Fiat 500e, Lease over
2016 Spark EV, Lease over