You're retired and you've finally got time to travel. Given that you likely have a more limited amount of disposable income than you did when you were working, using frequent flyer miles or points could be the way to go. But miles aren't like cash and first you'll need to do some research – not on how to earn mileage, but on how to burn it.

To quote Randy Petersen, aka the Frequent Flyer Guru, who operates WebFlyer and other mileage-centric web sites,You must have a plan when considering using an award to a popular destination. Fortunately, that planning is often perfect for retirees, since it involves exploiting the flexibility many other travelers don't have.

You may think a good strategy is for you (and your partner) to join multiple competing frequent flyer programs. But actually, fewer is better. Consolidation is key to maximizing the benefits of FFP participation, explains mileage expert Tim Winship, publisher of FrequentFlier.com. A single account, he explains, offers the best chance to qualify both for elite status AND the most desirable travel awards.

Which airline to select may not be as tough a decision as some think. Many journalists and experts based in New York City, Los Angeles or Washington, D.C., assume that everyone has a range of airline choices. In much of the country only one major carrier is dominant; if you live in such a region or near a hub city for a major carrier, it may make sense to join that program, regardless of how you feel about that airline. It could be the easiest way to accrue mileage in the long run. Of course, you also want to ensure the airline you choose flies to the places you'd like to go!

Another advantage of joining a major carrier's program is that you can earn – and burn – miles on partner airlines as well. Even with restrictions, it's a distinct benefit not matched by most smaller carriers. For perspective, American lists 27 airline partners; Delta lists 26; and United lists 38.

Petersen's WebFlyer may be the ultimate portal, with dozens of Program Guides for specific airlines and a Mileage Converter that allows you to calculate the end result of moving your account from one frequent flyer program to another. One of the site's most valuable tools is Ratings & Reviews, which offers a wealth of rankings (both Petersen's and his readers') on nearly all travel programs, and even provides side-by-side comparisons if you're having trouble choosing between two airlines.

Once you find the right program operated by a domestic airline, there's good news and bad news. The U.S. airline industry has undergone tremendous consolidation in recent years; just since 2001, TWA, America West, Northwest, Continental, AirTran and US Airways have been acquired, respectively, by American Airlines, Delta Air Lines, Southwest Airlines and United Airlines (also see 5 Iconic Airlines That No Longer Exist). The upside is that the largest domestic programs offer the most extensive route maps. But the downside is that the members from all those acquired or combined programs are now competing with you for tickets and upgrades.

However, if you're a retiree with a flexible schedule, you can travel to destinations most business travelers don't visit, and you can fly when most families are not vacationing.

Originally, the only way to earn frequent flyer miles was to fly. Now, however, there are almost limitless ways to rack up miles without ever boarding an airplane. One of the easiest methods is to select a charge card or credit card that generates mileage with your purchases (see Top Airline Miles Credit Cards). "Nowadays, most card companies and banks offer a plethora of rewards in terms of points, cash back or airline miles based on the amount of money the owner spends, a September, 2015 LendingTree survey noted, adding, 52% of Americans are clueless about credit card rewards.

"Having powerful cards with big sign-up bonuses is the easiest way to jumpstart your points strategy, says blogger Brian Kelly, aka The Points Guy. After you get the card, you can uses its rewards portal to easily earn affiliated airline miles and points by shopping at its online vendors (some even let you shop at brick-and-mortar stores, too). Among the major programs:

• American boasts of more than 1,000 partners in the AAdvantage program, including credit card vendors, restaurants, retail shops and companies representing industries ranging from communications to wellness.
• Delta's SkyMiles program lists more than 100 partners for everything from wireless providers to Broadway show tickets, and its SkyMiles Shopping site touts over 500 merchants.
• United's extensive list of MileagePlus partners includes over 850 retailers and companies in all sectors of the travel industry, including hotels, car rentals, rail, cruise and vacation packagers. [L18]

For more, see Best Ways to Save on Travel Using Airline Miles.

Ironically, the hardest thing to use your frequent flyer miles for often turns out to be – a flight.

While the Big Three (American, Delta and United) may offer the most partnerships and destinations, there is empirical evidence they lag behind smaller U.S. carriers when it comes to redemption.

In May 2015, the travel marketing firm IdeaWorksCompany released its sixth annual Switchfly Reward Seat Availability Survey, which analyzed 7,640 booking requests from 25 airlines worldwide. Here are the rankings and total percentage of seat availability for six domestic airlines (note: in some cases, there were ties with foreign airlines, not shown):

#1. Southwest, 100.0%

#5. JetBlue, 87.1%

#7. Alaska, 80.0%

#8. United, 75.0%

#11. American, 67.1%

#16. Delta, 57.9%

This should give you some idea of how difficult it can be to secure seats.

Consider these pointers from the guru Petersen:

• Start early. Based on years of research and tens of thousands of actual award redemptions, the optimal window to buy is six months prior to departure. Any earlier, and you may not access all of the available award inventory; any later, and you could be out of luck.
• Be flexible about dates. Monday, Tuesday and Wednesday are the best days for domestic flights, while Friday and Sunday are the worst days. WebFlyer.com also provides the best and worst days for travel to or from the Caribbean, Mexico, South America, Europe and Asia.
• Watch your flight. If you would like to home in on a particular route, consider using a fare prediction tool such as FareCompare.com. If fares rise, the awards availability should increase.
• Be persistent! If using the airline's online booking tools produces a negative result, contact the carrier's award redemption desk by phone and speak to a human. Even if this incurs a fee, it could be well worth it if the rep finds seats when you couldn't.

How much is a mile or point worth? The "exchange rate" fluctuates. Thankfully, ThePointsGuy.com provides monthly updates with valuations for more than 30 airline, hotel and charge card programs. For October, the site values range from half a penny on the low end to 2.5 cents on the high end.You should use such benchmarks when calculating the relative worth of the cost of a trip in miles or points.

For example, ThePointsGuy.com estimates Southwest's Rapid Rewards points are valued at 1.3 cents each. A recent search for a flight from Dallas to Houston via Southwest returned fares of $79 (or 4,226 points) for a non-refundable economy seat and $240 (or 25,217 points) for a Business Select seat. Using the benchmark of 1.3 cents, the cash value of the points would be $33 in economy and $194 in Business Select. In other words, both bookings cost less if you use points, but the economy seat is the better bargain.

It always pays to know the cash value of such transactions because in some cases it may not make sense to redeem your miles, particularly during a special sale on fares. Of course, there may be times when you'll choose to overpay with miles or points simply to use them before they expire. But as Winship states: As with dollars, your hard-earned miles may be spent wisely or foolishly. Or: Just because you can afford it doesn't mean you should buy it.

Every industry creates cottage industries, and frequent flyer programs have spawned online mileage managers that can offer help with organizing the details of your participation in these programs. Some are free and some charge fees.

Here are four of the many options you can consider:

• AwardWallet
• mileBlaster
• TripIt
• UsingMiles

Even though the fight to redeem airline awards has gotten tougher, retirees with flexible schedules are better positioned than most travelers to take advantage of them. It just requires a little research (and a lot of patience) to seek out the best deals.