I've got 8 minutes on my 18350 AW IMR. Voltage shows 3.7/3.6 either way. Just tested.
For there to be a true test, someone is going to have to read the voltage to more that a tenth of a volt. The Semovar doesn't round up, meaning if it's 3.79, it will read 3.7. Or, it could be 3.81, and read 3.8. That leaves quite a bit of "room" for voltage readings.
I'm getting between 6 and 16 minutes on my brand new purple Efest 18350s. If there is some logic to the difference, I am clueless. I'm in the house all day, temperature is the same, 9W, display=2, no led on the button, spring facing the battery, microcoil at 1.3ohms - which has not been changed in months. All I do is untwist the battery cap, and slide in a new one. I marked my batteries, and the issue does not track with the battery.
My charger displays two digits after the decimal, so maybe I can start tracking that. Not sure what I would learn from that...
The good news is that them there little batteries charge a whole lot faster than they discharge in the mod.
Oh, well. My KFL+ is now two weeks, at least, on the same rayon. That, makes me happier than long battery life. Much rather change a battery than a wick or a coil. And if I have to travel out in the scary wide world, an 18650 still gives me between a full day and two full days.
And, then there is the sticker...