In the near future, this business will only be about the "support"...figure out how to make a living based only on your expertise, not on selling stuff.

This is an interesting statement. With the state of components now a days being as sketchy as they are this gets more and more true every year.

I only do large projects as well so 1st year I cover labor and then I cover parts as per the manufacturer warranty. Not a problem.

The only issue I come across is the occasional homeowner that thinks changes are warranty items. You can cover yourself by creating a detailed scope of work and system functionality document at the time you make the sale/sign contract. Any additional requests by the homeowner are then documented via change orders and emails so that they can't say later on that they were under the impression that the system would do this or that when it was never intended to.

delete

How do you deal w/ and bill for tech support calls and remote support issues?

(how do I listen/watch X, the internet/cable isn't working, security system fault, etc)?

At a previous position, systems over an $X value could purchase 3 & 5 year 'gold' support for a percentage of total cost. This included 24/7 phone support w/ truck rolls for critical systems, next day service otherwise. Also covered replacement and re-installation of failed products, and where possible, a loaner part to cover downtime.

Generally, for a large or very large system purchase, I think this is a good option for a customer, and reasonable for the integrator with the following caveats:
-systems need to be exceedingly well engineered and documented
-need solid VPN access for remote support, and products that can be debugged (error log, live view of events and user actions, etc)
-tech's in this program need to be well compensated and empowered to resolve issues, and integrator should always be trying to onboard additional support into the rotation.