RHEL 7 Subscription Management on secure private networks

We have over 500 RHEL 7 subscriptions for our multiple servers at multiple remote sites. Due to security requirements, they are all connected together on a secure private network with NO internet connectivity. These servers will only receive manual locally installed updates/patches every 18-24 months due to the proprietary custom software that they are running.
My question is how do we (1) manually/locally disable the registration nag warning or (2) register/manage the subscriptions for these servers? And, using a dual-homed (private/internet) Red Hat Satellite server is unauthorized.
Thank you for your assistance.