When I took a few cooking classes and a well known culinary school, I had two chefs discuss this at length...one of which insisted that 75% or more of taste was through the sense of smell. The other chef held to the notion that it was at least a 50/50 balance between taste & smell for the brain to decide if you liked something you ate. Here are a few articles that explains a bit of the relationship between the two.
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When I was just starting out smoking cigars in my late teens, I noticed one of my Uncle Nick's friends doing something that I do to this day with almost every cigar I smoke. He did the standard charring of the cigar and then took a series of small, quick puffs to get it going. At that point he took the cigar out of his mouth and held it about a foot or so away from his nose, chest high, and waved the smoke from the burning cigar towards his nose and inhaled. He did about 4 or 5 waves of the hand over the smoke before I asked why he did this. He said, "I'm setting the table for my pallet so I can get the full enjoyment of the cigar." Pretty cool I thought, but still thought he was a nut...UNTIL I did it myself and found he was completely correct. I find I get a good handle on what the cigar will taste like before I start smoking it...and when I do retrohale, it's the back end of my exhale and I don't do it on every pull on the cigar. I find with the stronger Nicaraguan puro cigars, they can burn the receptors in my nose to the point I don't pick up much flavor. Haven't you ever walking into a room where one person is smoking a cigar, not a room full of smokers, and you took one smell and said to yourself, 'Wow, what a nice, fragrant stick that is.' Or conversely, 'What a nasty smelling cigar that guy is smoking.' To that point alone, you realize how important the sense of smell is with enjoying a cigar. Try it and see what you think.
To take this further, I have always found that during a multiple cigar smoking day, the retrohale has to be used sparingly because of the taste left behind from doing so. When we discussed on a previous thread the times we smoke multiple cigars within a day, when you consistently retrohale, you can't smoke a heavier cigar before a milder cigar...to me, if I do so, I find the second cigar's taste is changed by the residual amounts of flavor left behind from the stronger cigar.
On a single cigar day or evening, this is not an issue.