What you have to worry about is that the BMS was reset to hide the actual state of the battery (like in this posting: viewtopic.php?f=44&t=14285&start=1820#p527350
). That is, it might not really have 12 bars.
Just as a comparison, my 2013 SL at 31K miles has 12 bars and is at 86% capacity. It will likely lose a bar after the next winter. My summer range is just over 70mi. My winter range tops out at around 55mi. Another 2013 owner at work has over 60K miles and his battery is over 95%, so it's not impossible for this car to actually have 12 bars.
Note that range is vastly affected by your driving style. I get 4.5mi/kWh in the summer now. When I first got the car, and before I learned to chill-out my driving style, I got 3.5mi/kWh. That results in a huge difference in range. If you don't make that adjustment, you might find the real world range to not be sufficient for your needs.
As SageBrush suggests, a good test drive is best to guage the health of the battery. I think the best way to do this is with a OBD-II dongle and LeafSpyPro, and then put on as many miles as possible to really see the range of the battery.