The American Airlines Advantage credit card provides plenty of incentives for its continuous use.  For instance, bonus miles  are given at the one year anniversary, and if you spend $10,000 your second year, you not only get the 10,000 miles that go with it, but you also get an additional 10,000 miles, for a total of 20,000.  Then there are surprises along the way.  I got a postcard that stated that if I use my card at least 30 times over a period of about 2 months, that I'd get a bonus 3000 miles.  I've taken advantage of these bonuses and have been able to earn miles twice as fast as with...