Any benefit to establishing device trust over different subnets?

Our DNS setups involves 2 F5 DNS devices in our main location (call it 10.33.x.x) and one DNS device in our backup location (10.83.x.x) GSLB works and all is fine on that end but I'm wondering if I should add all three devices together as device trust members.  I've done the two in the main location  but I don't know if there will be issues with adding the backup.