I'm sure someone more qualified will jump in on this, but I'll take a crack at it. For myself, I use it for around a day, or until I feel a difference from "normal" or acceptable
vaping quality. Some people think that you don't want to completely discharge the battery, to extend the lifetime of them.
You will notice a difference from that fresh battery "feel", and the feeling after it has been used for a while. My advise is to go with your preference to when it is time to recharge.