how long account must be opened before one can file bankruptcy

In terms of a credit card account? Well, the time it is opened is not the focus.  The focus today is on whether or not you shopped 'till you dropped and then filed bankruptcy.  So, in essence, the focus is on the reasons for the charges, amount of charges, frequency, rather than when the account is opened. 

Read the following from freeadvice.com:

Can I use my credit cards?

You can never use credit cards after filing unless the court specifically permits it. If you continue to use the cards prior to filing, it is likely that the debt will not be discharged.

Can I get into trouble with balance transfers?

Transferring balances between credit cards can be a way to lower your minimum payments or to get a lower interest rate. When you do this, you’re actually paying off one debt and incurring a new debt. If you don’t have the present intention to pay the new debt (and if the creditor can prove you didn’t), that new debt could be found to have been fraudulently incurred, which would mean you couldn’t get the debt discharged in a bankruptcy.

Try to avoid using so-called “convenience checks” or other ways of borrowing on the new credit card to pay off the old cards. These “checks” are treated like cash advances. Cash advances within 60 days of a bankruptcy filing are presumed to have been obtained by fraud. Some bankruptcy courts have looked to see how the proceeds from the “check” were spent. These courts have then determined that obtaining cash in order to transfer balances is not fraudulent. There’s no guarantee that every bankruptcy court would reach the same result, however. Plus, you would have to carry the burden of proof to show that you intended to pay off the amount of the advance.

Can I keep some of my credit cards?

Applicable only in Chapter 7 cases, some credit card companies will allow you to keep allow your card with a lowered credit limit if you repay some of your debt. In fact, some companies will automatically send you or your attorney a proposed reaffirmation agreement while your case is pending. These agreements are generally a bad idea because they require you to promise to pay some amount of your debt (which is destined to be discharged if you do nothing) in exchange for a minimal amount of new credit. After your discharge, you are paradoxically going to look like a better credit risk than you do before bankruptcy. This is because you won’t have any debts. On the other hand, you will probably have to agree to pay a much higher than normal interest rate on new credit cards. If you always pay your credit card balance in full every month, you will never incur a finance charge, and the high interest rate won’t hurt you.

https://bankruptcy-law.freeadvice.com/consumer_bankruptcy/300/

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