Everyone is different with the level of nic they are comfortable with, and it does not depend on how much they smoked. It depends on how often you hit, your particular oral-absorption rate, how big a hit, and other details. With vaping most of the nic absorption is oral and in the throat and nose. With smoking analogs, the nic is carried to the lungs on ash particles. Nic effect is fast with lung, much slower with oral, but over time you can still get the nic.
My point is that there are many factors involved, and one simply has to play around with the levels until they find the level they are most comfortable at. Even 24 mg is too much for me for more than a few hits. It will make me jittery and sick feeling if I try to stay at that level for a whole cart, unless I cut back on how often I hit. For me 24 mg would be a hit every 5 minutes or so. 12 mg is where I am most comfortable for most of my vaping.
Additionally, many people in the beginning experience withdrawal from not getting the other components of tobacco that are psychoactive, such as the MAOIs. This generally passes in a week or two, but it can also make you irritable and jittery.
I would try cutting back on the nic a bit, but also be patient. It took me about a month before I got the feel of how much nic I should vape, and that level can change throughout the day for me. How one hits makes a huge difference too. The more vapor you see on the exhale, the less nic you are actually getting. Each little vapor droplet is a solution of nic and PG or VG, and maybe some water too. I pull vapor into my mouth, inhale a little, then very slowly exhale through the nose. Sometimes I inhale and just hold it. Its all getting in that way, but it might take a couple minutes to feel it. If I did that with even 24 mg, I would get pretty buzzed.
I would get some VG or PG and dilute some of it to 50%, maybe even more, so that you are at 15 mg or less, and see how that goes. Of course this will dilute the flavor too, but you will get an idea of what level you like the most. The initial few weeks of vaping can be a challenge, as you are looking for your nic "sweet spot". If you don't want to dilute your juice, I would buy a variety of juice strengths and play around with them.
In the beginning, many people also suffer from analog withdrawals, which are jittery and irritable feelings. Generally this is because the new vaper is using too little nic. It seems like you are not in this camp, though, as 30 mg is quite high...I am leaning towards you cutting back a bit...maybe a lot. Few need or can handle 30 mg.
