Comfort

• Your own comfort level might help you determine when it is best to use or save your frequent flyer miles. When using your miles, you will be placed in coach class. This can become quite uncomfortable if you are flying for more than four hours. If you can stand sitting in coach for the duration of the flight, using frequent flyer miles is likely the best option.
  
  

Busy Season

• High season is an excellent time to use your frequent flyer miles. When the number of travelers begins to go up, so do ticket prices. For example, flying from New York to Los Angeles at Christmas time or over the summer months will cost the flyer nearly twice as much as any other time of year. Provided that the airline doesn't place any restrictions, these are great times to cash in those miles.
  
  

Shoulder Season

• Off-seasons can also provide opportunities to use frequent flyer miles. During the shoulder seasons, the availability of seats is greater, so the chances of using your miles rise. Do the math before you make a decision. On average, a free domestic ticket through most airline frequent flyer programs requires about 25,000 miles. Most airlines calculate the price per mile at about 1.2 cents. This equals a dollar value of approximately $300. Check the prices of the airline tickets. If you can find it for less than 300 dollars, you might be better served to buy the ticket.
  
  

Financial Crisis

• In times of financial crisis, it might be a good idea to start cashing in those frequent flyer miles. If an airline is facing bankruptcy, the person holding the miles is considered a debt. Depending on the decision of the bankruptcy court, the holder of the miles might be a creditor that doesn't receive payment. In other words, you might lose your miles even if the airline doesn't go under.