Templates are great for very standardized cookie-cutter networks.
For existing networks, you need to be aware of what configuration will be overwritten in the network when you bind your network to the template. It will almost certainly require some downtime to reconfigure some specifics (Eg. VLAN's, IP's, Site-to-site VPN settings). If you are uncertain, you can always create a new test network and bind it to the template to see what is impacted.
However, if your networks have a current or future requirement to differ from one another, I instead suggest keeping them separate and using the API to push bulk updates to multiple networks.
It has a slightly higher learning curve but is much more useful/powerful.
