What is the best design to handle Workgroup Folders?

Currently we are doing things like this:
- There is one special account for this purpose.
- This account contains a Mail Folder, a Calendar, etc for each team.
- The permissions are bound distributions lists.
- The distribution list contains all team members.

Everything is working fine. But now, we would like to throw our IMAP Workgroup Folders into the Zimbra Workgroup account.

Can one account handle about ~50GB Mails and more? The teams would only see some parts of it. I know about the Outlook PST limits. When do things become crazy?

So long,
Aiko