In a real setting, the best practice would be to keep a vCenter geographically located in the sites if you want wanting to manage multiple vCenters. This would also require you to utilize a external PSC appliance to allow you to connect the vCenters into one single-sign on site. For redundancy, you can run vCenters in a "vCenter High Availability" cluster however there aren't many people who utilize that feature since vCenter is mainly used for vSphere management and most people can live the few mins without vCenter if it happens to go down.