I 'overdid' many times during my first month of vaping. This was partly due, I am sure, to the fact that many times I simply did not have to find a place to vape like I did when I smoked. SO instead of having to go outside I could just vape away at my desk, etc.
Now knowing that what was the satisfying part of the nicotine was the feel from the spike I realized that what I had been doing by almost chain vaping (probably like the other poster to assure myself I was replacing the analog) was adjusting my body to a high base level of nicotine and then when I would vape a bit more for a spike feeling - then I got jittery or even nauseated.
My final adjustment, since I happened to like vaping away was to use a nic juice with a low level of nicotine in it and then when I had a urge, vape a bit of nic juice at a much higher level. I actually have started to chain vape 0 nic juice, and when I get a nic jag using the mod with the 24mg juice in it. That way I get the same spikes that satisfied with analogs without keeping a higher level in my blood so that when I 'spiked' it up I was getting too much nic.
It is really a guestimate when you switch from analogs to vaping as to what nic mgs will be right for you. The idea that a heavy smoker needs the higher level nic juice and the moderate of light smokers needs less is just a starting point. A heavy smoker, for example, could run the gamut of puffing the whole analog up to allowing most to burn up and only taking a few hits - and so the level they have is vastly different.
The real 'meter' for what nic mgs you need is you and what your body tells you. If your vaping a lot because you enjoy seeing the vapor but are getting jittery or feeling green then you probably do want to lower your nic level, or learn to put down the PV after a few minutes instead of 15, so you mimic your smoking intake.
You will get a handle on what works for you and what feels right for you. As an analog smoker your body adjusted to cigarettes and learned to signal when you needed one and when you had too much, when you needed to only hit the stick a few times, or puff away down to the filter. Your body knew when it wanted you to inhale very deeply, create a great TH or just inhale shallowly and limit or avoid a TH. Your body did not learn this overnight but came about with smoking over a period of time and it will take some time - and everyone's adjustment/re-learning time differs - for your body to start getting signals straight.