I came to terms with a concept: I switched to vaping from smoking. I didn't quit a satisfying recreational activity.
Unless you plan on quitting vaping, lowering nicotine levels is kind of a moot point. Nicotine wasn't the unhealthy part of your former smoking habit. Why deny it then? Scratch that itch brotha!
Find the coil build/nic strength that gives you the ability to have a vape, and then feel satisfied enough to set it down; not something that is sub-par and you have to puff manically on. You remember those super stressful times where you would say to yourself: "Man, I need a ... cigarette...." and you'd step out and have a smoke? Try to find the coil build/nic strength that fills that role unquestionably. It does indeed exist.
My setup:
Reo + RM2 (1/16th air hole)
Twisted 28g micro coil @ .6Ω-.7Ω
18mg-22mg nicotine (DIY 90% VG)
I've been running Reos with this kind of setup for about 6 months now. Works like a charm. I find that I use it and it hits like an actual cigarette. The hit, the warmth, the vapor production, the mouth/lung feel, the appreciable quick onset of nicotine satisfaction; everything but the ash, stink, and cancer.
Cravings come less and less when you start to realize you've actually found something that exceeds what the real cigarettes did for ya drag for drag.
Cheers