I recharge mine after 23 miles, which is also about 2 of 4 lights on the battery gauge. My normal route is 23 miles, so I don't think the battery would last two trips, and I sure don't want to have to pedal this beast home with no assist, LOL. BTW, with only 4 status lights, when 2 are lit, it could be anywhere from 50% remaining (optimistic) or very close to 25%. I think the battery gauge on the bike's display is more of a recent average, than an overall average.
I have assumed the charger is smart, so I just plug it in and do not monitor it. If I think about it, I'll try to unplug the charger when the status light turns green, but often I forget and unplug it the next day. The charger gets warm when charging, but is completely cold to the touch in a few minutes, after the status light turns green.