Who sir you don't want to use them until they're completely discharged, it decreases the life span. Instead use them until they get to a point that vapor production is starting to seriously decline then stick them on the charger.
So this mean one should stop before the LED starts flashing?
I still have difficulty knowing whether it is the battery or the cartomizer that needs replacing, so I tend to vape til it flashes. Sometimes I sorta know, and will try the same carto on another battery or vice versa.