How to Keep Your Frequent Flier Miles From Expiring

Darren Booth | CNBC

Frequent flier account balances can be zeroed out for inactivity. But there are cheap, easy ways to avoid this from happening. And they don't require flying.

During the past decade, most airlines instituted mileage expiration policies for travelers who don't have some type of activity on their account within a certain time frame, generally one year to 18 months. Flying is the most obvious way to earn miles. But travelers often overlook everyday activities that earn or use miles, in turn preventing mileage balances from going "poof!" (Read more: Frequent Flier Miles Vanished? Here's How to Get Them Back)

Here are my tried and true methods to ensure my frequent flier account balances never expire.

1. Credit cards: For the two airlines I fly the most — American and United — I use credit cards tied to their frequent flier programs for everyday purchases. Why not earn miles at the grocery store, gas station or even Starbucks?
2. Shopping online: Most airlines offer online shopping portals linking you directly to online retailers. After signing into your frequent flier account, look for shopping links under an airline's "earn miles" webpage. Most major retailers participate with airlines, including Amazon and Apple. Buying an iTunes song? That $1 purchase is definitely the cheapest way to extend the life of your miles.
3. Dining out: Similar to shopping, most airlines offer a dining program. Money spent at participating restaurants earn miles. They may not be upscale restaurants, but I've never had a problem finding a decent place that participates in mileage programs.
4. Renting a car: When making a car reservation online, most major rental companies have a field to enter your frequent flier number, thereby earning you miles for the rental. And if they don't, ask at check-in.
5. Staying in a hotel: Similar to rental cars, hotels allow mileage accrual for paid stays.
6. Taking surveys: I have to admit this strategy is a bit annoying as my time is valuable. But I did sign up for two survey programs through United with e-Miles and e-Rewards. Both are free to join and provide bonus miles simply for signing up. At the completion of a survey, you can earn roughly 100 miles for sharing your opinion.
   
7. Magazine or newspaper subscriptions: And most airlines have tie-ins with popular magazines and newspapers where you can redeem miles for a subscription.

Overall, the trick is to ensure an accrual or redemption of miles posts to your account before the total balance expires. And keep in mind each transaction resets the date your miles expire to a future date, thereby extending the life of your miles.