Best Practice : Archivelink and Content Server

We have one content server up and running with one repository for purchasing documents. We are about to turn on archivelink functionality for some SD outputs. What is the best practice, one content server with many repositories (i.e Z1 (purchasing) Z2(sales orders) Z3(invoices) or a different content server/repository for each module such as purchasing and sales and distribution.

If you use Archivelink/Content Server, I would appreciate any feedback regarding your landscape and how many content servers or repositories you have.

Thanks,

Carla Matczak