According to the BMW i3 book that's been around for awhile, a single charge from 0-100% puts the same wear on the battery as ten charges of 90-100%. Personally, I just plug mine in when I get home, and leave it. In the six years, my battery range is slightly lower, but not much. If the car is plugged in, you can leave with a full battery if you decide to precondition it. While you can condition the cabin without being plugged in, in the winter, you will also find it useful to precondition the battery pack, and that requires it to be plugged in. That battery warming process can take up to 3+ hours. You'll use more percentage of your charge when the batteries are not conditioned, so in theory, you'd be putting more wear on them by not preconditioning them by setting a departure time. Using round numbers, say you can go 100-miles when they're conditioned and you go 20-miles. That's a 20% usage. But, if you do not precondition them, the car might go 80-miles in the cold, and you go that same 20-miles...that's now 25% of your capacity putting that much more wear on them.
The battery management in the car will not use the real full capacity on either end, so the batteries are never really fully charged or discharged before the readout shows 100 or 0%.
Unlike a simple phone charger, the power gets shutoff by the car when it thinks it is full.
2011 535i x-drive GT, 2014 i3 BEV