Since I've been
vaping (> 6 years), I've heard that most of the nic in vapor is absorbed in the mucous membranes of the mouth, throat, and nose. I don't know if there have been any scientific studies that document that as being true. Theory is the nicotine molecule in vapor is larger than the nicotine molecule in smoke, so the vapor molecule may not get into the lung's tiny alveoli (air sacs) for absorbtion. So in theory, its not necessary to inhale vapor into your lungs to absorb your nicotine.
It's also probably benefitual to exhale some of your vapor out of your nose. Our sense of smell works closely with our sense of taste. You can probably relate to this when you have a really congested nose and you temporarily can't taste your food or drink.
Since many recent smokers have damaged taste buds from years of smoking (vaper's tongue), exhaled vapor out of your nose can help you "taste" the flavors in your vapor. Often I can taste one flavor component of the
juice while inhaling, and another flavor component during the exhale.