16 from 8 is a good jump. Challenge now is seeing wifey smoking and want to join the fun.
I got her a mod today. We will see how much she uses it but I'm optimistic.
I wouldn't think of it as a jump.
For example normal cigarettes are supposed to only provide about 10% of the total nicotine level they contain via the inhaled smoke. This is normally indicated on the box itself, tested by a standard machine test. The average is 1mg a cigarette depending on brand. However, based on researches and tests,the nicotine intake by a human from one cigarette varies from person to person and even cigarette to cigarette. It can double or treble that amount, or on the contrary, lower, depending on different factors. For example, according to one reseach, the body is capable of absorbing greater amount of nicotine in the morning from a cigarette than at other times of the day, possibly due to the higher demand for nicotine. Another example is that changing the brand of cigarettes to lower nicotine content doesn't mean you'd absorb less nicotine from that cigarette, on the contrary, more likely the same as the cigarettes with higher content. The less number of smoked cigarettes a day is the best approach.
So where does vaping stand here.... We don't know how much nicotine first of all is being transferred from the e-liquid to the vapor, depending of course on type of e-liquid. Second, this will also depend on the e-cigarette kit quality/brand/type of automizer combined with this e-liquid. And third, even if hypotetically the first two factors are the same for everybody , the personal factor of how you vape and how you inhale comes into place which may increase or limit the amount of nicotine absorbed.
So, if 8mg of juice are causing cravings and making you smoke real cigarettes, then don't be afraid to get a juice of higher nicotine content. It doesn't mean you'd be literally taking in double the nicotine content.
And on another hand, although nicotine has its big drawbacks, it actually has quite an impressive list of proven benefits and unless you intend to quit all type of nicotine products altogether, it probably makes little difference whether you vape 8mg or 18mg nicotine as far as health is concerned. It's actually the only thing that can be considered "good" in real tobacco smoking. Your body will tell you when you've had enough of it and you should eventually be able to identify the correct level. Then lower gradually once you are stable on vaping without the real cigarettes.