People that are majorly addicted usually light up before their feet hit the floor.... I myself could go until the afternoon before the cravings would hit.
Apparently theres a study that show people who light up first thing in the morning will have blood/nicotine levels several times higher than those that wait a few hours.... even regardless of how many smokes they have throughout the rest of the day.
You make a good point. I was able to quit cigarettes very easily, I would go all 6 hours into my day before smoking my first analog. My roommate would smoke before he got out of bed. I would have to admit he smoked more daily and by generic conclusion, probably is more addicted to nicotine vs. me. He would also probably have a harder time quitting than someone like myself.
I have done 0 research on how genetics play into what percentage/levels of nicotine are absorbed by different people. I want to guess it is much like everything else, genetics will have a say on how chemicals effects people on the individual level. For example, after a period of no drinking, I get drunk off one beer, another friend takes 2-3 (Both weigh close to 140 but I am 0.5" taller). I have a lack of a enzyme in my blood that breaks it down thanks to genetics.
So far what I have read on the internets, I doubt there is a difinitive answer to how nictine is absorbed by everyone. I assume it is more based on the individual. There are so many factors the only conclusion that makes sense to me is it is different for everyone. Example factors: how and if using a filter, strength of drag, how one makes a drag, how long one holds it in, ppm of nicotine in vapor/smoke, the "filler" of the smoke/vapor, one's genetics, one's quality of lungs and levels if foreign material, and probably many more given the time to write them all down.