We've had not dissimilar requests to hold years of dailies on disk.
Normal we highlight that there is a finite limit on the number of restore points within a backup or backup copy GFS set...
This limit varies dependent on the storage and application being used, but it's always going to be there.
IF there really is a business case for Continuous Data Protection, Journaling or Extended data retention for a service than there are more appropriate solutions out there than keeping backups.
Get the business to underwrite the costs of researching those.
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