The answer to this question is as often as you like. However, you cannot receive a Chapter 7 discharge if you have obtained a Chapter 7 discharge within the past eight (8) years. You calculate the time period from the date you filed your last Chapter 7 petition. The date you actually received your Chapter 7 discharge has no bearing on the calculation.
However, remember that the goal of Chapter 7 bankruptcy is to obtain a discharge. As defined by the United States Court website:
A bankruptcy discharge releases the debtor from personal liability for certain specified types of debts. In other words, the debtor is no longer legally required to pay any debts that are discharged. The discharge is a permanent order prohibiting the creditors of the debtor from taking any form of collection action on discharged debts, including legal action and communications with the debtor, such as telephone calls, letters, and personal contacts.
Although a debtor is not personally liable for discharged debts, a valid lien (i.e., a charge upon specific property to secure payment of a debt) that has not been avoided (i.e., made unenforceable) in the bankruptcy case will remain after the bankruptcy case. Therefore, a secured creditor may enforce the lien to recover the property secured by the lien.
Please keep in mind that the discharge takes care of your personal legal obligation to pay your debts. You can still make voluntary payments if you want. Additionally, a secured creditor may still recover his collateral, but the secured creditor cannot obtain a deficiency judgment. The most common examples of secured creditors are vehicles and residences.