(NPN/RNN) - You might have done it yourself - signed up for the credit card just to get a special offer and then not used the card again after you nab the introductory bonus.
But now some banks are cracking down and making it more difficult to earn when you "churn."
It's affecting people like Stephanie Miley who never had the cash for her dream trip to Hawaii, so she started signing up for credit cards to earn the trip for free.
"An 11-day trip, including airfare and hotel stays, we would have had to save up for years and years," Miley said.
She stacked up the cards and earned free flights from one and a free hotel from another.
The practice is known in the banking worlds as "churning."
Consumers apply for credit cards specifically for large sign-up bonuses like cash, points or miles, and once those bonuses have been earned, that card is abandoned and it's on to the next one.
Credit card churning can give thousands of points worth thousands of dollars in redeemable value, and can help you travel for free.
Sean McQuay of NerdWallet said the banks offer these bonuses to bring in new customers, and they don't want them to cancel - or "churn." Some are now starting to crack down on the programs being exploited.
CitiBank gives bonus points only to consumers who haven't opened or closed the same card within the last 24 months.
American Express restricts even further, allowing only one bonus per product per lifetime.
And Chase representatives say "customers who open multiple card applications in a short period of time, regardless of issuer, will likely encounter difficulties."
"They're struggling to find ways to clamp down on churning without really turning off consumers," McQuay said.
Banks are also hoping to cut down on what is called "manufactured spending." For example, buying gift cards with your bonus credit card just to pay off the bill that same money.
"Banks are quickly clamping down on these," McQuay said. "Now, at many checkouts, you can't buy gift cards with credit cards because they're trying to stop that activity from happening."
Manufactured spending also includes when you earn points by paying a friend via a payment app like Venmo, PayPal or Square, and then have your friend pay you back.
As for Miley, she said she's fine playing by the rule, but she plans to continue flying high with her travel bonuses.
"I think part of the fun is the challenge in it," Miley said. "Finding that deal, finding that great card, and then saying 'Yeah, we got this entire trip on bonus miles.' How great is that."
Experts say credit card companies can negate any bonus points earned if they think you're trying to game the system. There's also potential hits to your credit.
Each time you open a card, there's a credit check, and having a lot of new cards will decrease your average length of credit, which can lead to a drop in your score.
Finally, there are potential fees is sending money via a third-party payment app.