The enemy of any battery is heat. Cells get hottest as they near full charge. This can be mitigated by not fully charging (i3 only charges to 94% on 60Ah models), charge tapering (i3 BMS can slow charging is warranted), and active cooling (check).
If you have the time to spare between drives, you can always select to charge at a reduced rate. I nearly always charge at 16A / 120v, not out of concern for battery health, but because it's what's available at work. That rate barely registers as a blip on the battery temperature readout.
I don't know what Level 2 rate begins to creep into "abusive" territory for the i3, but by all accounts I've read, the car does a good job taking care of itself, leaving not much to worry about.
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