A way to calculate the relative value of spending airline miles on merchandise instead of travel is explained quite clearly in a recent post on The Dallas Morning News’ Airline Biz blog.
Customers who hold frequent flier miles may feel compelled to use them to buy things this way, even when it’s clearly a bad deal, because the airlines have shortened expiration periods. But if you think you’re forced into a “use them or lose them” situation, you should consider other ways to create activity in your account and thus keep your miles valid for another 18 months or so.
The Rewards Network dining program is any easy way to do this with Alaska, American, Delta, Midwest, United and US Airways. One meal out, perhaps at a restaurant you would have visited anyway, and you can reset the time clock on your miles. (You can earn credit on Southwest, too, though its program works differently.)
Donating money to the Haiti relief effort is a particularly commendable way to earn miles on some airlines. Donating miles is another way to keep your account active. The Los Angeles Times’ Daily Travel & Deal blog has details.