In recently lost over 3,400 miles on US Airways because I didn't have any activity. I received mail from them saying my miles were nearing expiration but I didn't act quick enough to keep them from expiring. Unfortunately those miles are now wasted. However if I'd found some way to generate activity on my account I could have kept the account active and saved the miles.
Before I've found that there are often fairly cheap options available to generate some new mileage activity on your airline miles account and keep your miles from expiring. You might even find a free option to get miles.
Free Miles promotions
First thing I'd do is see if I can find a promotion offer for free miles. On occasion airlines will offer free miles if you sign up for their newsletter, fill out a survey or something along those lines. I've seen a few such promotions on the Fat Wallet Forums. So you can look their to see if there are any current free miles promotions. You might also try searching google for "free miles" plus the name of the airline, for example "free miles united" might turn up some offers to get free miles on United. The free promotions are pretty random and hit or miss so I wouldn't count on them, but it is worth alook. If you can't find a free mileage promotion then it may be worth paying a few bucks to generate some miles.
Cheap Miles Options for Major Airlines
Here is a quick run down of the expiration policy for major airline miles programs and a recommended cheap option to generate some new mileage activity and avoid expiration of your miles:
Alaska Air: - Expiration : 24 months
Cheap Option : Use Alaska Airlines Mileage Plan Dining and eat at Burger King or other cheap restaurant
American Airlines AAdvantage - Expiration : 18 months
Cheap option : Donate to UNICEF
Delta Skymiles - Expiration : 24 months
Cheap Option : Use Skymiles Dining program and eat at Burger King or other cheap restaurant. OR shop at a merchant in their Skymiles Shopping program and buy something cheap.
Southwest Rapid Rewards - Expiration : 24 months
Cheap option : Unfortunately there really isn't any cheap way I can see to avoid expiration.
United - Expiration : 24 months
Cheap Option : Use Mileage Plus Dining program and eat at Burger King or other cheap restaurant.
Other airlines
I haven't looked through all the airline miles programs. If you have miles on a program that is not on this list then look at the program partners and see if they have any options to make a donation, do some online shopping or eat at restaurants as those are likely to be the cheaper options to generate some extra activity.
Is it worth spending money?
If you don't have at least a few thousand miles it may not be worth spending money to keep the miles active. A few thousand miles is probably worth spending a few bucks to keep. If you figure that an airline ticket usually runs $250 or more then 25,000 miles to get a ticket would mean that miles are worth approximately 1¢ each. If you have 5,000 miles then that has an approximate cash equivalent value of $50. The 3,400 miles I lost from US Air were worth roughly $34.
You may have to act months in advance.
Some of the cheap options I mention above can take 6-8 weeks to credit your account with the miles. If you have miles due to expire then you should act sooner rather than later in order to try and keep the miles active.
Next time you have a fair amount of airline miles expiring, try and find a cheap option to