Banks are free to limit withdrawals from "savings accounts" (accounts that pay interest) as they wish in order to preserve their cash. In effect it varies bank to bank (of various types of bank) and from time to time (they can change their policy when they wish). Furthermore, from the FDIC: " What is the grace period for the FDIC? After the lapse of the six-month grace period, the deposit insurance coverage of the account will depend on the ownership category in which the accounts are now held. "

In other words all a bank has to do in a bank run is merge with another bank even to get the FDIC insured money back to the depositor. Search on "bank run". Banks are free to scream "bank run" anytime. It's not just 6 months in practice...it's more. We saw this in 2008-9 if you remember. These laws and regulations are still good as far as I can see. (Some regs were repealed in 2020 having to do with withdrawals more than six a month -- but still allowed by the individual banks). The above quote came from the FDIC today. The practical consequences for the depositor become very real once banks start to run out of cash in bank runs.