It is true that the quantity of nicotine in e-juice is much higher than is present in natural tobacco and the absorption rate is less. And yes this is due to the particle size of the vapor being much larger than the particle size of cigaret smoke (so the nicotine particles from a cigarette are exposed to a larger surface area of the lung, increasing the rate and amount of absorption). Also, as mentioned, nicotine binds to propylene glycol and glycerine and this delays absorption. But these do not answer the posters question.
The poster stated that they found the vaping experience satisfying, but that the craving to vape again was more frequent than with a real cigaret. There is an explanation for this. The positive feelings that are induced by nicotine are primarily due to the release of dopamine, the "feel good neurotransmiter". Whenever you are feeling good your brain cells are releasing dopamine, but the brain has to be able to modulate itself rapidly depending upon the environment. Soon after dopamine is released, it is broken down by an enzyme, repackaged and sent back inside the cell. Tobacco smoke contains a substance the inhibits the enzymes responsible for the breakdown of dopamine, therefore the dopamine hangs around for a longer period of time. Pure nicotine lacks this substance, so although there is a surge in dopamine release, that dopamine is rapidly broken down so the pleasurable effects are of a shorter duration.
One possible solution that may help is using e-juice that contains menthol. Menthol delays the breakdown of nicotine and increases nicotine blood levels.
One poster suggested that most of the nicotine from vaping is absorbed via absorption in the mouth and nasal passages. DON'T try this on yourself, but I find if I draw the vapor into my mouth, do not inhale into my lungs and slowly expel the vapor through my nose, the "hit" is more intense. It burns like crazy the first few times, but that is how I vape, 1st thing in the morning. It's akin to snorting in a sense I guess. Off course that's just my subjective experience.
Hope this maybe informative to some. This is my first post so sorry if the formatting, etc. Is not correct.