Are you a frequent-flyer packrat? It may be time to start cashing in your chits. Consumer Reports' travel team researched the frequent-flier programs of 11 U.S. airlines and Air Canada. It's conclusion: Airline bankruptcies, blackout dates, tighter rules, increased mileage requirements, and shifting partners may be putting your precious miles in jeopardy.

The good news is that most miles last longer -- indefinitely in many cases -- than in the past, when they expired after three years. Mileage-earning opportunities have also increased. You can rack up miles from earthbound partners like rental car outfits, hotels, florists -- yes, florists -- and credit cards like The Motley Fool Visa. According to CR, travelers earn roughly 40% of their miles without ever leaving the ground.

Here are six commonsense keys to making sure you cash in.

1. Focus, focus, focus. Don't spread your travel across multiple carriers. Choose one or two airlines for your earning power.

2. Be that flexible, fly-by-the-seat-of-your-pants traveler you claim you are to your shrink and Sig. O. You're more likely to land an award -- even a cheaper one -- if you're willing travel on weekdays. Just 20,000 miles can earn you a domestic ticket through U.S. Airways if you travel off-peak -- a mere 40,000 miles will carry you to all the way to Europe.

3. At the same time, it pays to plan ahead. Some award seats are available as much as 331 days in advance. Then again, you never know if your airline will be around that long. The good news is that airlines have relaxed their cancellation policies.

4. Lose the paper. Being a tech-savvy e-ticket shopper can occasionally earn you double miles and other perks.

5. Free is as free does. You may have to use double your miles to get the seat you want in some programs. Again, travel flexibility is key for those who want to use the lowest-cost award tickets.

6. Brace yourself for the cattle car. Consumer Reports says it's getting harder -- and more costly -- to use award miles to upgrade your ticket. If you buy a full-fare ticket on United, you'll need 16,000 miles to move up a few rows. For restricted tickets on American and United, expect to part with 30,000 miles. Call ahead, and remember to stretch your calves before boarding.