thank you for your question.
If you reach the limit (with requests or processing units - unless you don’t request very small areas, you will most probably run out of processing units first), you can simply drop us an e-mail to email@example.com with the additional quota you would need for that month and we can configure those additional requests/PUs for you to purchase via the dashboard.
If you need more volume for several continues month there is also always the option of upgrading your account to the next level.
Do note that the Exploration plan you are referring here to, is meant for non commercial/Research purpose only.
I hope this answers your questions