Interesting thread.
I started on 24mg liquid. It turns out I vape like a crazed monkey when I'm working. After lots of headaches and tiredness, I dropped down to 18 or 12 mg juice.
I definitely get less headaches from this now. However, I find if I can't chain vape when I want, I start to get moody or snappy.
I might need two rigs, a quick hitter rig with heavy nic content, and a desk chain vape rig...
Typed on my mobile. Please excuse typos.