I've probably bored the Dickens out of most of you with my rantings about resting, aging, final fermentation effects, etc. Most people just want to smoke cigars and not be bothered with whether it's rested, or aged, or whatever. Most of us just want to walk into our B&M, or bust open our latest online purchase and spark-up. Sadly, most who do this are oblivious to how a truly, properly-rested cigar tastes.
First off, ammonia is a byproduct of fermenting tobacco. Tobacco is fermented several times during the manufacturing process. The blender sniffs and tastes the mature tobacco, comes up with his masterpiece and sends it off to the roller. Here's where things get dicey. All that "perfectly aged" tobacco has to be re-wet in order to roll. This wetting kicks off another, final fermentation, which can last up to two years after the cigar is rolled. It gets even trickier than that! You can grab a cigar, straight off the rolling bench and smoke it and never taste the slightest hint of ammonia! This is simply because there hasn't been sufficient time for fermentation to occur, thus, no ammonia! It's only weeks, even months afterward, that the ammonia begins to be released.
Depending on how mature the tobaccos and how aggressively they're wetted, this ammonia can be anything from a kick in the face, to a very subtle, "off flavor". Ammonia is not easily detected by the tongue, but very easily detected by the olfactory sense. The ability to train the mouth to detect what the nose knows takes years.
Here's my quick and dirty method for discerning ammonia (and therefore an immature cigar). Light the cigar as you normally do and smoke it down until you've warmed the wrapper. As you smoke, smell the warm part of the wrapper. The heat will release whatever ammonia is left in the cigar and you will definitely smell it! One clue is if the cigar tends to taste a little "dry" or astringent. This is a motivator for me to sniff behind the cherry and more times than not, ammonia is revealed.
I try to leave everything alone for about a year, before I smoke it. In rare cases, I get really new cigars that haven't had time to enter the final fermentation and I will smoke one... and they can be fantastic. BUT! There is no getting around the fact that, eventually, every cigar will enter a final fermentation and release ammonia. Let them have a good nap. The result will be ever-so worth the wait.