Based on your subscribed plan, there will be a cap to the number of checks you can perform per month. These will only apply to create check requests - other requests do not have a quota besides rate limits.
The service quota is outlined below:
Plan
Monthly Service Quota
Standard
2,000
Custom
Check with your Account Manager
Request over the service quota will return a 429 Too Many Requests error.
You can check your monthly service quota consumption on your plan settings page.