For years, travelers have been told to collect airline miles, save them for a dream vacation, and eventually turn a large balance into free or heavily discounted travel. But many frequent flyers are now asking an uncomfortable question: Are airline miles losing value every year? The most accurate answer is more complicated than a simple yes or no. Airline miles do not automatically lose a fixed percentage of their value every January. In fact, some recent analyses have found that the average cents-per-mile redemption value of several U.S. airline programs has remained relatively stable or even increased. However, travelers can still experience a very real decline in the purchasing power, predictability, and usefulness of their miles. A flight that once required 25,000 miles might eventually require 40,000. A valuable partner redemption can disappear. Award seats may become harder to find. An airline can also change the rules governing how rewards are earned or redeemed. So while the v...