All the Airlines seem to be both giving away more and more frequent flyers miles but also making it harder to use the programs. Through credit card offers, not to mention actually travelling on planes, you can rack up hundreds of thousands of miles – enough for many trips. Unfortunately it’s not easy to use these so you’ll need to strategize a bit, plan travel far in the future to obtain most of the lowest miles deals, and MOST IMPORTANTLY, you’ll need to hang on to your miles.
I just used a nice offer by American Airlines to extend my wife’s miles for 18 months. She gave away 1000 miles to the “Miles for Kids in Need” program at AA, and this kept her from losing the rest of them. Here’s the link to AA’s charity miles giveaways: http://www.aa.com/i18n/AAdvantage/redeemMiles/charities.jsp
Another way to preserve your miles is simply to buy 1000 miles for about $30 from AA. http://www.aa.com/i18n/AAdvantage/purchasingMiles/main.jsp
One of the WORST things you can do is let them expire and then pay over a penny per mile to have them reinstated – unless you have a very specific use of your miles, in my opinion it’s not worth, say $200 to keep 20,000 miles. Some would (wrongly) suggest that the calculation would be along these lines: “You can get a $400-500 ticket for 25,000 miles so they are worth about .02 each”. The problem, however, is that you usually CANNOT get a ticket easily with miles and also you won’t tend to have exactly the right number for a tickets, leaving some unused or you unable to use some. So my rule of thumb is that miles are worth about 1-2 cents per mile assuming you travel and lot are will use them.
FYI “selling and buying miles” is a risky proposition. I’ve not done this and the laws seem fairly complicated, but I think you risk losing miles if you try that game.