Q: My frequent-flier accounts have been inactive for too long, and my miles are going to go down the drain. What's an inexpensive last-minute save?

Q: My frequent-flier accounts have been inactive for too long, and my miles are going to go down the drain. What's an inexpensive last-minute save?

A: Inactivity periods can creep up on frequent-flier members, especially since some major airlines have been reducing the amount of time fliers' accounts can rest idle — no miles earned or redeemed — before wiping clean program members' accounts.

American Airlines' 36-month inactivity period switched to an 18-month limit on Dec. 15, United Airlines will make the same switch on Dec. 31 and Alaska Airlines will cut its inactivity period from three years to two years starting April 1, 2008.

Other airlines' inactivity periods range from JetBlue Airways' one-year expiration date to Continental Airlines' indefinite commitment.

But saving miles is easy — no need to rely on travel to earn miles. A program member can shop, eat out, take a survey, watch an online ad, donate miles to charity or order magazine subscriptions to add mileage to an account in small increments, keeping it alive.

"It's hard to believe that we would be talking about frequent-flier programs and someone's worrying about their miles expiring," said Randy Peterson, publisher of InsideFlyer magazine. "Virtually any activity counts toward extending your miles, all of which are pretty easy and pretty everyday."

Leisure-time solutions such as holiday shopping with the airlines' retail partners or eating out at one of the thousands of restaurants linked to major airlines' flier programs require little extra effort or spending.

"All of the big programs these days have what I call mileage malls, which are networks of online retailers," said Tom Winship, a frequent-flier program expert. "The larger such malls comprise up to 200 and more online retailers." To use these malls, program members must first go to the Web site of the airline on which they want to accrue miles and click through to the retailer's site via the mileage plan window.

To use a dining program, register a credit card number with a mileage plan (free), then pay for meals with that card.

Purchasing groceries can also net miles — United, for example, has a relationship with several major grocery chains.

Transferring miles to another account or buying up miles are not good deals, said Winship and Peterson.

Many airlines charge 1 cent per mile transferred, with an additional transaction fee. On Northwest Airlines, for example, transferring the minimum 5,000 miles would cost $75, with no additional miles gained.

Alaska requires a 1,000-mile minimum purchase when buying miles directly — not a bad deal for $25, plus taxes — but gaining free miles via regular purchases and activities has more value.

"You would be hard-pressed to think of anything that you might want to buy that you couldn't earn miles for," said Winship. "Many of these online malls have in place right now bonus mile promotions that go through Christmas."

Many major airlines' program members can also sign up with Web sites erawards.com and emiles.com. Sitting through a short ad or filling out an online survey posts 10-15 miles per activity to a previously-specified airline, ensuring that infrequently-used mileage accounts don't die.

And while miles stored in American's mileage program expired on Dec. 15 if the last activity registered was in June 2006, the airline offers a one-month grace period, until Jan. 15, 2008, for program members to redeem or earn miles and win back expired accounts.

If all else fails, some airlines offer mileage reactivation. American can retrieve expired miles through December 2008, at a cost of $50 for every 5,000 miles, plus a processing fee; Alaska's reactivation, available up to a year from the day of expiration, costs a flat $75. United does not currently offer a reactivation plan.

On the Net:

www.e-miles.com

www.e-rewards.com