i would never leave
batteries unattended ... but, I throw on RCR's overnight and they normally turn green within 2-3 hours. Pop them off in the morning ....
Assuming you're home or nearby, I see no issues. Leaving them for extended periods of time and you aren't around, I would hate to see your house or workplace burned down. I pull
batteries off when I won't be around.
Better to be safe than sorry!