With extra visitors enabled, this feature would allow you to keep Justuno active, even if your website met or exceeded it's session limit
At a Glance
What is the extra visitors feature?
Basically, it's akin to a limited cell phone carrier plan; if one exceeds the limits of their plan, in lieu of shutting Justuno down, it will continue to run while incurring charges.
Login to your Justuno account, and activate the feature here:
Note: Charges do not roll over to the next usage cycle
Note: Prices may vary based on discounts applied at the purchase of your plan