Some credit cards offer a sign-up bonus in addition to the regular rewards program they offer. Think of it as an extra enticement for applying and using the card. The bonus could offer rewards points, miles or even other types of perks. But to qualify for these sign-up bonuses, you generally have to reach a certain spending threshold within a specific time period after opening the card — usually around three months.

A card that charges an annual fee is more likely to offer a bigger sign-up bonus than a card that doesn’t, and travel rewards cards often offer greater sign-up bonus opportunities than cash back cards. But there’s no guarantee that a bonus that offers more points with a higher spending requirement will be more valuable to you than a bonus of fewer points and a lower spending requirement. The value of points or rewards can vary across programs, so you’ll want to do the math to make sure it’s worth it.

Additionally, bonus offers sometimes expire or change. If you see an offer that interests you, don’t assume that it will be around forever.

One last thing to consider: It’s not worth going into debt to get a sign-up bonus. When you’re thinking about which card to apply for, look at your regular spending habits and try to match them up with a rewards program and sign-up bonus that makes sense for you.

Rewards points and miles are valued differently depending on the rules of each program as well as how and when you redeem them. For those reasons, it’s tough to assign one set value to a point or mile — they might vary quite a bit based on the rewards program and redemption options.

For instance, a rewards program might allow for redemptions in the form of travel, cash back (such as in the form of statement credits), gift cards and merchandise purchases. Some programs might make all points and miles worth the same amount — perhaps 1 cent — no matter how you choose to redeem. But that value might not always be the same. For example, one rewards program might assign a higher value for travel and cash back, but lesser values for all other types of redemptions.

Calculating the value of a point or mile gets more complicated if the rewards program includes the option to redeem points directly for travel bookings. The value of redeeming that point or mile will depend on what the booking would cost in money, and that amount might change depending on other factors.

For more info on calculating and assessing the value of your points and miles, take a look at our Credit Karma editors’ article on point valuations.

If you meet the eligibility and spending requirements for your card’s sign-up bonus, you’re likely to receive your sign-up bonus points (or other benefits) several weeks after earning them. The exact timeframe depends on the rules of the card or rewards program, but it’s usually listed in the terms and conditions. Unless it’s specifically mentioned though, it’s probably fair to assume you won’t receive your bonus immediately.

That means you probably shouldn’t expect to be able to use your sign-up bonus right away. So if you like a card’s sign-up bonus, consider its value as a long-term boost to your rewards rather than as a shortcut to immediate rewards that can be redeemed right away.

A sign-up bonus can be a useful, cost-effective way to improve your rewards balance or gain interesting perks. But it’s called a bonus for a reason. If you apply for a card primarily to take advantage of the sign-up bonus, you might find that the cost of maintaining the card eventually outweighs whatever value you received from the bonus.

That’s partly because the best sign-up bonuses usually come from cards that charge annual fees. While a card might waive the annual fee for the first year or offer a bonus with potential value that goes well beyond that yearly fee, you’ll still have the card even after you earned the bonus. If you find that you don’t get value out of the card’s core features and rewards program over the long haul, you’ll have gone to the trouble of earning the sign-up bonus with no clear long-term benefit.

It’s also probably not in your best interest to spend more than you can afford just to get a bonus. If you have to carry a balance because you went over-budget, you might end up paying so much in interest that it outweighs the value you earned from the bonus.

It’s better to consider how a card fits into your broader financial plan, rather than only focusing on how you can take advantage of an attractive bonus offer. If you find yourself applying for several cards just for the sign-up bonus, you’ll likely end up with dips in your credit scores due to hard credit pulls — and a hefty bill of annual fees.