Scheduled Systemstate backup best practice

Hello,

I have a question about best practice with scheduled backups for System State. I'm using wbadmin in a scheduled task. 

The domain is two DC, server1 which is also fsmo holder and server2, one forest, one domain, and an Exchange 2010 server. A second site will be add in the near future.

Is there any best practice about the schedule when we have two or more DC, two sites  ? for example to schedule the fsmo holder after the others DC or something like that ?

I can't find this information.

Thanks in advance

Yannick