Agree with zefoy, the retention period of the recycle bin is held by Microsoft and we cannot change it.
As a supplement, if we want to preserve files or items in SharePoint Online that are deleted more than 93 days, we can create a Retention Policy or a Retention label to retain them.
For example, if the content is modified or deleted during the retention period, a copy of the original content as it existed when the retention settings were assigned is created in the Preservation Hold library.
If you want to learn more, see:
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