ambient temperature matters on the 2013 leaf. When I had it during the winter (40 F in the mornings @ 7am, over 50 F by 10am), my SOC would rise by almost 3% just from the change in temp! So I would guess that the reverse might also apply if temp drops significantly enough from one test period to another.
2nd data point. I left my leaf unplugged @~50% on a long weekend trip - 4days. When I came back, the SOC was still ~50%. So yeah, there should be zero self-discharge.