Never, ever ever is it a good idea. Here's why....

1. Every time you do so you give the lender permission to pull your credit. The inquiry is of the "hard" variety, which means it might hurt your scores. If it does, the damage lasts a full 12 months. Inquiries don't diminish in negative value with time as other derog data does. Why take the chance to save a few bucks?

2. The credit limit on retail cards is normally very low. This means that with even responsible usage the card is likely to be more "utilized" than you'd normally keep another card. Again, this can hurt your credit scores. So, why take the chance? This is ONGOING damage, not just damage at inception.

3. The rate on retail cards is not determined by straight credit risk like that of a bank issued Visa or MasterCard. That means your rates are likely to be disproportionate to those of your other cards, especially if you have good/great credit. E.g....My lowest FICO score is 807 (and has been right around there for almost 15 yrs) and every retail card I've ever opened has rates in the high teen or 20's. That means if you ever do revolve a balance then you're likely to chew away any savings you realized.

4. Retailers make money from the sale of the merchandise in addition to their lending arm making $$ from interest. That gives them the flexibility to offer 10%-20% off. Their goal is to get their card in your wallet. Then they go to work on you. Do you really want that?

I've had it out (almost physical) with CFPs who argue that with proper planning and timing there's nothing wrong with doing this. My arguement is that you don't know what you don't know. You have no idea if you'll need to rely on your credit reports and scores some time in the next 12 months for an emergency loan, job application screening, auto or homeowner's insurance...or what if your car poops out on you and you need a car loan? Any damage you've done to your credit and scores will far outweigh any benefit. Do some math...figure out what an additional 50bps will do to a 30 yr fixed mortgage of $300,000. It's never worth it.

And it's even less worth it when the issuer is offering coffee mugs and t-shirts at the airport in exchange for you applying.

I'll make you a deal Erin...let me know the next time you go shopping and I'll send you $25. That's probably close to 10% of what you were going to spend. I'll sleep better knowing you didn't use your credit report as a coupon.