Does anyone know the maximum number of mail accounts that can be used with the 'accounts' parameter during a restore operation?

I have 3,000 plus mailboxes backed up from a single mailbox server that I will be migrating to a multi-server environment with 3 mailbox servers.

My mailboxes vary from a few MB to multi GB for active users. I am thinking to split my mailbox list into 3, balancing for number of mailboxes and mailbox size. I would then want to run CLI commands to restore the mailboxes to their respective new servers. I doubt the CLI will accept 1,000+ email addresses at a time.

I guess I could figure this out by trial and error but it would be helpful if someone has the answer.