IMHO, it doesn't hurt to charge the thing daily, or leave it on the EVSE. But, the only time you could hurt the battery pack is if it was low, cold out, and you didn't recharge it. In normal, temperate weather, you do not need to charge it daily. I just find it handy to always have it full when I leave.
Assuming the information is correct in the i3 electronic book, available for free, recharging 10x from 90% puts the same wear on the battery pack as recharging it once from 0%. The i3 is not your typical cellphone battery type or charging circuit. And, unlike most devices, the car literally completely disconnects the acv inputs once it's happy. It may turn it back on a few times to balance the cells, but once fully charged and happy, it may not turn the EVSE back on for a week or more to top off. There's some hysteresis in the system of, I think, at least a couple percentage points, and the standby losses are quite small, assuming everything is working properly.
2011 535i x-drive GT, 2014 i3 BEV