Hello,
I think you have to solve this with scripts.

You can determine tapes with a write data older than three months and do a checkout for them.

Have a look at the Tape Vault, this is a good structure to maintain the life cycle.
https://helpcenter.veeam.com/docs/backup/vsphere/tape_media_vaults.html?ver=120

You can administer the vault(s) per script, too.

You can do both daily and monthly tape backups.  For monthly you can create GFS pools to handle the ones you need to move offsite along with the scripting mentioned.

See here for more details on tape and media pools - https://bp.veeam.com/vbr/3_Build_structures/B_Veeam_Components/tape.html

Great comments above. You would need to script it.

I use the Tape Vault when I export tapes, but I haven't scripted it yet. I manually export my tapes, and alternate sites.   Once the retention is up I put them back in while at the site.

GFS Media pool is great as you can have your weekly / monthly land on the same day if you want.. rather than creating 2 pools and using double the tapes that week. 

GFS media pool, exporting and Tape Vault when you are done will get you in the right direction though. 

@hs08 , can you elaborate on your workflow more? You state the data needs to be moved off-site after 3 months, correct?

So you should have:

1. Copy of data on disks → Max 3 months
2. 3 months after creation date, the backup must be moved to an offsite location
   1. Does it matter how?
   2. Do you need to wait to ship the tapes?

I must be missing something as I see that scripts have been recommended a ton but I’m not exactly sure that the workflow I understand needs any scripting.

Media Sets organize your tapes automatically in a way that is convenient for shipping the tapes to some tape storage location, so just start both primary backup jobs and tape jobs, and once it’s time to ship tapes out, just find the relevant media set, export its tapes, and ship it to the tape storage.

I’m pretty sure media sets makes this way easier for you to know which tapes reflect which month and get them out, and I think having local redundancy with Backup Copy is probably better, but I think explain your intended workflow more, I think there is not enough to tell you a complete strategy personally.