Not really. Why?
There are however limitations on SQL (really large ones, but still) in regards to 'number of items and changes to a database'. These are described in (I believe) the Performance Guide, or the Best Practices for SQL.
As FY, I have been in an (mailbox/journal archiving) environment with >100.000 active archives, and over 100.000.000.000 items, total size >400TB
Do you mean recommendations for single EV Servers?
As far as I remember the recommendation was arround 4000 Exchange mailboxes > 1 EV Server
althought I do not know if this has changed over the last few years.