There is no way for the user to change the backup retention policy of Time Machine, and I'm not aware of any third-party apps exist that extend it with that kind of configurability either.
The third-party apps that do exist can only flip Time Machine on and off for you to achieve a less frequent backup schedule than hourly. There is one on the AppStore called TimePreserver to manually back up your backups, but it cannot be run as a scheduled service.
You could potentially write a maintenance script to run periodically that would open the Time Machine server and copy off the hourly backups for safe keeping elsewhere. But then to recover that information, it's unclear to me whether it would be as simple as copying the hourly backup files back to the Time Machine server and trying to access them via the Time Machine client interface. This is something that you might test before writing the script.
You could also try preserving the hourly backups on the server-side by doing something similar with your own Linux-based Time Machine server or Time-Machine compatible NAS. You'd just have to create your own way to keep hourly backups from being deleted (an hourly maintenance script that copies them to a separate location or manages file permissions or something).