I'm not sure of the cutoff points as I really never hit cutoff on either device.
What then are you using to Determine - Not lasting? Flavor Drop off?
I've used several Brands of 18350 Batteries. Unusual things I have noticed:
Higher Drain 800mAh - Last longer in Mechanical mods
Lower drain 1200mAh - Last much longer in Regulated Mods
*We are only talking about 2-3 amps and not pushing to limits.
There is also the limited possibility you simply have a defective cell. It happens, even with the best of brands.
As to Charge cycles - Most new batteries have to be cycled several times before establishing their full Charge cap and drain level. 4-6 is plenty.
What is worse is some lesser design mods have issues with sinking to true battery level. I've been through that with a few earlier Regulated mods. A few battery removals and restarts usually correct the problem.
Also consider excessive drain due to possible poor contact. A Regulated mod(PWM) will quickly draw down a battery trying to maintain correct output with a weak connection. Vape will drop off even with some decent charge available.
I clean with alcohol and on occasion a fine sandpaper.