I am brand new to vaping. a few weeks ago I bought a iStick PICO and bought a EFEST IMR 18650 2500 mAh 35A. I have been doing a lot of reading and I read that I shouldn't let it drop past 3.7 volts. With my PICO that's at like 3/4 of the battery bar. Am I right to not let it drop past 3.7 volts or can I use it until the low battery warning and then charge it? Does it matter? I am very confused.