Hello Hamdhan Azeez,
Thanks for your question.
Yes, the second API call to retrieve the analysis results using the operation location header is chargeable. They apply to the analysis itself
Storing the operation location in a database for future calls will not save costs
See: https://azure.microsoft.com/en-au/pricing/details/ai-document-intelligence/
Official expiration time is usually 24 hours.
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Regards,
Abiola