Just today I sat in a co-worker's 2013 S with 46000 miles and 12 bars. A full charge said 21.2kWh and it was at 62.5AHr. I was quite amazed it was in such good shape compared to mine. I didn't get his build date, but his is about 6 months older then mine (built 12/13). We both keep it in a garage at home and under a parking garage here at work. We both only trickle charge at home, and use the same EVSEs here are work. We have comparable L1/L2s counts -- mine is 1200 and his is 1500.
The big difference is QCs: I have 60+ and he had only 3.