In Azure AD Monitoring and Reporting documentation and the SC-300 Study Guide (Module: Monitor and report on identity and access) , sign-in logs in Azure Active Directory are retained for a default duration of 14 days.
The sign-in logs contain information about user sign-in activity, including application usage, conditional access policies, and multi-factor authentication details. These logs are accessible through the Azure portal # Azure Active Directory # Sign-ins, or programmatically via Microsoft Graph.
Microsoft specifies:
"Azure AD stores sign-in activity for 14 days by default. For longer retention, you must integrate with Azure Monitor (Log Analytics), Azure Storage, or Event Hub." This 14-day retention limit applies to tenants without additional premium log retention solutions.