Period End Closing can be done n number of time too.
In normal business scenario, after year end closing also we need to adjust some entries (by passing some journal entries) w.r.t Auditing. Once we pass a journal entry to the Expense and/or Revenue accounts, then the Year End closing must be performed in the company again.
Once Period End Closing is done, you can revert back to the level before PEC by restore our backup. However, you may perform more than one PEC. Be careful when you do it the 2nd or nth PEC. A trial balance need to be run with satisfied result before you click on the button.