You can update your bank account at any time. However, if your payout is already in transit, it will be paid out to your old bank account and not to the new account.
Stripe creates payouts in advance of their post date to ensure that funds reach your bank account on the date that they are expected. If there is a payout showing in your Dashboard as in transit or paid, updates made to your bank account information will not retroactively apply to these payouts and will only apply to the next payout.
If the bank account your payout was sent is closed, the payout will return to Stripe and be paid out to your new account. This can only happen when the funds actually arrived back to Stripe.
If you updated your bank account while a payout is in transit, wait 5 business days before getting in touch as it is highly likely your payout will return to Stripe.
You can check the status of your payouts from your Dashboard.