Image:  Stack of Credit Cards © Fuse, Getty Images

Are you too plastic for your own financial good? Although there is no magic number of credit cards that should be in your wallet, some key questions can help you determine whether you're charging around town with more plastic than you need.

According to recent data from Experian, the average U.S. consumer has three open and active credit cards. Whether that is too many, too few or just enough for you is really a question of how you use and manage your accounts.

If you have the tendency to spend more than you earn, you might need fewer than three credit cards -- and maybe none at all, says Harrison Lazarus, a financial consultant and founder of Harrison Lazarus Advisors. On the other hand, if you spend well within your means, more credit cards could be good for you. "You will be able to access money when you need it, obtain fringe benefits like rebates and mileage, and improve your credit score," Lazarus says.

If you are unsure (or in denial) about your spending habits and general attitude toward credit, here are some warning signs you have more credit cards than you can handle:

1. You pull your annual credit report and find open credit cards you had forgotten about. Do you open a store credit card every time you hear the words, "save an additional 10% if you open an account today"? Do you mail back credit card applications in exchange for offers of bonus miles? If so, chances are you have credit cards lying around that you have not used since the day you signed up.

Rod Griffin, the director of public education at Experian, says open accounts that you have neglected could increase your risk of identity theft. Cards that are left idle could be stolen and used to make charges long before you notice that they're gone.

If you have unused credit cards that you don't want to close just yet (more on that in a moment), Griffin says it's best to lock them away or keep in a safe deposit box in your bank.

2. You are not paying your credit card bills on time. You know you have too many credit cards when you start having bill payment issues. If you carry 10 credit cards, for example, and you use all of them, you have 10 monthly statements to deal with each month. "Having too many credit cards can lead to the lack of time and focus to ensure proper credit card management," says Kimberly Howard, a certified financial planner and owner of KJH Financial Services.

Every credit card requires a payment date, and each one could be different. Payment juggling could lead to missed or late payments, Howard says, which could ding your credit scores.

Even just one credit card might already be too many for you. "The total balance on all cards compared to the total credit limit on those cards is called the utilization rate," Griffin says. "A high utilization rate, whether you have one card or many, is a strong indicator of credit risk and will significantly impact credit scores."

3. Your credit scores have been dropping steadily. Several factors influence your credit scores, including your previous payment performance, your total outstanding debt and how long your credit accounts have been open.

Inquiries and new accounts can also adversely affect your scores. Every time you apply for a credit card, an inquiry is added to your report. This pushes down your credit scores a little. "An inquiry is viewed unfavorably because it means you are shopping for credit," Lazarus says.

To find out if the number of credit cards you own is a reason for your low credit scores, pull your credit report and look at the risk factors. If "too many revolving accounts" is listed, it might be a good idea to forgo future card offers and think about closing some already-open accounts.

4. You are having a difficult time getting a loan. Having too many credit cards could be among the reasons if you are denied a mortgage or car loan. Howard says loan officers nowadays frown on borrowers carrying more than five credit cards.

Even if you maintain zero balances on a handful of open cards, you can be considered a credit risk. "The loan officer realizes that you could use all of your credit cards after the loan is approved, and that will affect your ability to repay the loan," Howard says.

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High credit scores alone should help prove you are worthy of loan approval, but Howard says that's not the case now. Since 2008, loan officers have been far more careful in approving loans, she says. "They are favoring mostly those with a limited number of credit cards, in addition to having a high credit score."