How to prevent your miles from disappearing

If you think your frequent flyer miles won’t expire for three years, you didn’t get the memo: Most airlines have replaced the three-year rule with new policies limiting the life of miles to either 18 months (American, United, US Airways) or two years (Alaska, Delta).

The harsher policies mean travelers must make an extra effort to ensure their miles are not lost. But maintaining miles indefinitely is still easily done, and well worth doing.

Above all, remember that any account transaction—either earning or redeeming miles—extends the life of all miles in the account for another 18 months or two years. So, assuming an airline trip isn’t on the agenda during that time, the strategy is to preserve the already accumulated miles in the most convenient, cost-effective way possible.

To extend miles by earning, one of the best bets is making a purchase in your airline’s mileage mall. Simply buy something you already want at one of the many online retailers participating in that airline’s program. American’s mall, for example, includes more than 200 online merchants, including Bloomingdale’s, Circuit City, Dell, Gap, Lands’ End, Office Depot, Starbucks, Waterford, and so on.

And to extend miles by redeeming miles already on hand, most programs allow members to cash in as few as 400 miles for a magazine subscription. That’s a simple, low-impact transaction, and you get a year’s worth of reading while simultaneously preserving your frequent flyer miles.

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