One of the side effects of cigar smoking is a tendency cigars have for turning stronger and bitter in the last couple of inches. If this is something you can relate to, there's actually something you can do about it.
Construction, burn and draw issues aside, all cigars, regardless of their strength, build up in tars, nicotine and moisture as they smoke. In many cases, at least with some of the more complex blends, the flavors will improve and taste great right down to the knuckle, while in others, the cigar will begin to "turn," leaving a sour taste on the palate, at which point you're probably better off letting the cigar go. If you paid around $5 or more for the cigar, you might be hesitant to trash it, and there are some cigar smokers who will puff-on as long as possible, even if the cigar tastes crappy, if only to get their money's worth out of it. I have three words for that: not worth it.
There are a few things you can do to help alleviate this problem and get the most bang (you'll excuse the expression) for your buck.
The first thing you need to do is take notice of how you smoke your cigar. If you tend to hit on it a lot, the faster those tars will build up. If you draw strongly on your cigar, that may have a negative effect on its taste in the middle and latter stages. Cigars were made for relaxation, so do it! Take your time when you smoke a cigar, and let it smoke itself for a minute or so between puffs. This will allow the flavors to caramelize more slowly, and therefore, offer a much more flavorful smoke that will hold-up longer, as well.
The other thing you can do is when you clip your cigar, try to expose as much cap as possible. The more narrow or smaller the cut, the more likely the concentration of flavors will increase, hence more tars and nicotine, too. If you normally use a piercer, punch cutter or a V-cutter for clipping your cigars, they will tend to be stronger and hotter as you smoke. That's because the small cut size restricts the amount of smoke coming through the head.
One the other hand, cigars with tapered heads such as Torpedoes, Pyramids and Belicosos are purposely designed to do this. However, they also tend to be wider in ring gauge, so you have a lot more tobacco to filter the smoke.
Using a single or double-blade guillotine cutter or cigar scissors naturally exposes more cap, thereby allowing more smoke to get through and helps decrease the buildup of bitter tars, excess moisture and nicotine.
As noted above, the ring gauge, and even the length of a cigar can determine how much tar and nicotine will build-up. If you smoke Coronas, try smoking a Robusto or a Toro. If you smoke Lanceros, try a Lonsdale. Most cigar smokers tend to settle into a particular shape after a while, so if you're not willing to change your shape, try doing some of the other things mentioned above and you'll significantly extend the enjoyment of your cigars.