Retention for deleted Office 365 data can vary by the application. For instance, an Exchange Online mailbox keeps deleted items for 14 days by default, but this setting can be changed up to a max of 30 days. When using the SharePoint Online application within a browser, items deleted are retained in the Recycle Bin for 93 days from the time of deletion.
It’s worth noting that retention policies can take time to set up correctly and data loss can and does occur, due to human error during retention policy configuration. So, it’s vital to have a backup of Microsoft 365 data as an insurance policy.