Leaving the car plugged in for long periods after charging ends doesn't hurt the main/big battery - it can't be charged passed 100%. (Sitting at 100% charge can cause accelerated degradation in warmer weather, though.) It can, however, drain the charge from the little 12 volt battery, as the car checks periodically to verify that it's still plugged in, and it doesn't charge the 12 volt battery often enough to compensate for that drain.
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
BAFX OBDII Dongle
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.