The on-time payer

You make almost every payment on time, don't carry a balance, have been a loyal customer for years, and have a high credit score. You're not concerned about your card's APR because you don't pay interest, but you enjoy earning rewards—cash back, points, or air miles.

Suddenly, those rewards aren't so rewarding. For example, for domestic flights, some cards offered by Citibank and Capital One now require you to redeem at least 40,000 miles or points, up from 25,000. If you want to eliminate blackout dates and availability restrictions, it might cost you 50,000 points. Some cards charge stiffer fees to have points combined with airline frequent-flyer programs.

If you make two consecutive late payments on a Discover card, you lose all frequent-flyer miles. Beginning this past September, American Express Blue and Blue Sky cardholders who pay late lose rewards points earned for that billing cycle. If the account returns to good standing, the forfeited points can be reinstated for a $29 fee for each month of points that you want back. Citibank is adopting a similar practice. For late payments on Citi cards earning ThankYou points, rewards might not be redeemable until a customer makes all payments due. A reinstatement fee might apply for each late month (though currently there's no fee).

Perhaps you have little interest in rewards but keep a card for convenience, emergencies, and the consumer protections they offer in the event there is a dispute with a retailer about a purchase. During flush times, card issuers kept extending your credit limits based on your excellent payment history and high credit score. But recently some cardholders have seen those credit lines cut dramatically, which could ding their credit scores.

Ronald Duffy of Santa Fe, N.M., had the same Bank of America card for years and always paid in full. His credit line had been raised to $50,000. It was recently cut to $12,000. He protested, saying that his credit score would be lowered by the cut. "Bank of America said that the line of credit has nothing to do with my credit score," Duffy says. "I then called Equifax, and they said it does. Also, Bank of America lowering my line of credit may make it more difficult to get a loan, mortgage, etc."

What to do

• Use rewards quickly. Expiration dates and other restrictions can cost you points, so spend them before you lose them.
• Choose cash back over points or miles. With deeply discounted airfares, you might be better off buying a ticket with your cash rewards. If you're dead set on a mileage card, look for one that lets you combine your miles with a frequent-flyer program, such as Citi's PremierPass card, so that you can double-dip on points.
• If you pay an annual fee for a rewards card, make sure you use it enough to make it worthwhile. Consumer Action, an advocacy group, found that you'd need to spend $10,000 on the American Express Delta SkyMiles card, which has a $150 annual fee, to get $100 off on a Delta flight.
• Look for off-the-beaten-path rewards cards. Financial companies Fidelity and Charles Schwab offer cards with unlimited 2 percent cash back and no annual fee.
• Consider having your savings account and credit card in the same place. Chase and Citibank pay additional rewards for card customers who also bank there.
• Ask to have your old limit reinstated. It might not work, but 51 percent of the people in our survey who complained to their issuers about new terms that were imposed on their cards were at least partially successful in changing them back.