These cards are not for everyone. World travelers with plenty of flexibility can collect frequent-flier miles via their card spending and redeem them for business- or first-class airplane tickets to far-flung locales that would otherwise cost many thousands of dollars. I have personally received an effective 10 percent rebate on my card spending by doing this in the past, though it becomes much harder if you are anchored to school vacation calendars for 20 years. So a return like this is by no means guaranteed, not even close.

Our collective goal of becoming unprofitable customers also requires discipline, and not just the kind that leads to making payments on time, not carrying a balance and being careful to track points and miles. Plenty of research suggests that people spend more on plastic than they do when paying cash. Readers of this column are all above average, though, right? As are those researchers. In a column last year, I discovered that most of them have kept right on using their own rewards cards. One of them had a good suggestion: Use cash or a debit card for several months to establish your spending baseline, then switch to a credit card and stick to the budget.

Still, skepticism is warranted with 2 percent cards, since many other banks have tried these deals and failed. So I asked the issuers I have mentioned in this column if their cards were profitable. Fidelity readily admits that it pays for some of the rewards. So it’s a special case, though its card has also been around for the longest period of time, which suggests stability. Citi and Capital One both confirmed that their cards made money. Barclaycard did not offer an executive to speak to me, its main spokeswoman was traveling and an outside public relations representative sent me an email informing me that information about the card’s profitability was proprietary. As I said, skepticism is warranted.

Worried about the card companies making the rewards less generous right after you go to the trouble of switching cards and resetting all of your automated monthly bills? I would be, too, so I’ve tried to get the companies to promise not to change things. Fidelity guaranteed to me early last year that it would not change the 2 percent rebate for at least 18 months. This week, it reset that clock, so anyone who starts using that card now will be safe until November 2016, at least.

I tried to get Capital One, Citi and Barclaycard to beat that 18-month guarantee, but none would name a number. They all, however, offered various versions of this reply: We have no intention of changing it anytime soon.

Good intentions are nice and all, but if you want to earn the big bucks, you’re going to have to take at least a little bit on faith. Still, for a household spending $20,000 a year on a card, this is $400 in rewards. If you’re spending $50,000, that’s $1,000 extra in your pocket each year if you play your cards right.