Each API has its own limitation rules. These rules helps the service being more secure by returning error messages to the requests detected by the system's security rules.
Unlike other GeoIP service providers, the only limits we consider is sending more than 3 requests within 5 seconds. (The fourth request will be rejected).
So, you will be able to use the service as you want without any daily/monthly limits. Just DO NOT send more than 3 requests within 5 seconds.