Sometimes I end up removing the battery and putting it in a 2.5 to see the remaining voltage. I would also like it if there was a low battery blink and it didn't just shut off.
I don't go that far ... but when it gets into the 40's I consider it time to change the batt. I can vape it for hours from full charge 'till it show 'like' 42% ... then it seems to rapidly decrease from that point. (I use the black banded AW 18490's & they're all relatively new)