Lithium Ion
batteries like to be at some level of higher charge at all times. They die when they are allowed to go flat and left that way. You may notice that the vapor/taste is dropping off and suddenly the light flashes. The charging circuit in Joye
batteries shuts off before they are completely dead to prevent total discharge and doesn't completely charge to 4.2v. It stops at 3.92v which is the suggested charge point for long life. The voltage regulator in the battery maintains the
vape voltage under load at around 3.2v - 3.3v during usage.
So, you can charge when the light flashes or charge more often. I use my 510s and Egos until they flash unless I'm going somewhere and want to know I have full charge.