Right now I’m creating a nightly restic snapshot of my server on borgbase and on some spare drives, and keeping the snapshots forever. There’s a ton of daily churn in my data though, between databases and logs and other files that don’t constitute ‘real data’ but might be needed to restore the app.
As long as I have space. My backups are on dedicated drives, and as they run out of space the old ones are deleted.
I guess OPs question is more about what makes you comfortable.
Is your drive only big enough for 2 backups or is it big enough for hundreds? If it was half that size would you still be happy with the number of backups? A quarter of the size?