You will probably notice that your vapor is diminishing as the battery gets down to 3.7 -3.8 volts. I was worried about over-discharging mine at first, so was checking them a couple of times a day, I don't think I've ever gone below 3.7 volts, and I could tell they were not hitting as hard.
I would suggest checking them often until you get a feel for how fast they are discharging. Never let them go below 3.2 volts for sure.
I would suggest checking them often until you get a feel for how fast they are discharging. Never let them go below 3.2 volts for sure.