In my case I am my own customer, I am technically an installer but I only install for my own company. I am the IT/admin side usually but get out and install often enough. I also also have a crew or two that handles installs and then we have other guys that handle normal maintenance at our properties that can handle the basic stuff, cleaning, re-aiming, and even camera swaps as needed. Our camera system is pretty involved so just prepping NVRs, cameras and keeping stuff in stock is a full time job I swear!
We've already used over 60,000 feet of cat5 this year and I just ordered 25,000 more. All fun and games until it is work!