The current settings require reauthentication every 30 days.  

You will need to re-authenticate on your device & your browser after 30 days except for the following actions,

• Switching to a new browser 
• Switching to a new device  
• Resetting your login password  
• Clearing browser cookies (or using a browser that is set up to clear cookies after it is closed or is setup not to save any cookies) 
• Signing out of a Microsoft 365 application  
• Using an incognito/private browser window  
• Switching between two or more Microsoft school or work accounts registered with your Windows device  
• ILAC IT revoking MFA sessions if your device is lost or stolen 
• Your MFA settings are cleared and require you to re-register with MFA