No, there is no need to make any changes to your account while you are not touring. atVenu bills Per Touring Month on 30 day cycles. If you do not have any saved shows in your account for a 30 day period, you will not be charged. There is no need to cancel your account.
Once you start using atVenu again your billing cycle will reset and the credit card on file will be charged. You can change or remove the credit card on file at any time. There must be a credit card saved to your account in order to Settle any shows, however.
Also see: What does 'Per Touring Month' mean?