Should I use a separate DNS domain for the virtual infrastructure?

What are some guidelines for determining when you should create a separate DNS subdomain for hosts in your VMware infrastructure?

For example, I have DNS domain called

mycompany.com

All existing desktops and hosts are on that domain.  I'm going to have a combination of 1500 hostnames of ESXi, vCenter Server, vCenter server database server, and other VMware components.  As my infrastructure grows, at what point do I need to think about separating my VMware infrastructure hosts and putting them on a separate DNS domain from other parts of the corporate network?

Any thoughts/ best practices / suggestions welcome.

Thanks.