Exhcnage 5.5 Backup Best Practises

I am running exchange server 5.5 on NT4 using veritas Backup exec and the exchange agents.

I have inherited the setup with the agents set to backup the information store only.

I was thinking about turning on the Mailbox agent as well, but I am unsure of the ramifications of backup times and the benefits of the restore process should I do so.

Is it better to keep the existing setup or go to backing up the mailboxes as well and what benefits will I gain from this?