Hi artisticcheese,
I believe this article has got the answer to your query:
https://learn.microsoft.com/en-us/azure/security-center/security-center-using-recommendations
Security Center automatically runs continuous scans to analyze the security state of your Azure resources. When Security Center identifies potential security vulnerabilities, it creates recommendations that guide you through the process of configuring the needed security controls. Security Center updates its recommendations within 24 hours, with the following exceptions:
- Operating system security configuration recommendations are updated within 48 hours
- Endpoint Protection issues recommendations are updated within 8 hours