How long should I keep my local and off-site backups?

I'm currently using BackInTime and TimeShift to create local backups of my system and personal data. I configured both to keep 7 daily, 4 weekly and 6 monthly backups. I use this setup on my Desktop-PC as well as on my laptop.
Now I also use BorgBackup to create an additional backup of my local backups and right now use the same retention policy, so keeping 7 daily, 4 weekly, 6 monthly and 1 yearly backup.
This turned out to be a lot of data and my 1 TB off-site storage solution is currently using 953 GB of storage.
Now I was wondering if my double retention policy is even making sense and what others are using. So how long do you usually keep backups? How many backups do you keep and what would you suggest for my setup?