You my man should work for yourself. You will blow the competition away. This is the way I have been running my business for 23 years. Try asking a Hobart, GCS, or a Service Solutions man to change a ballast. You'll hear them laughing all the way to the back door. If there was enough guys like you and me and the customers knew their was life after warranty these other companies would be out of business. Warranty gets them in the door but the smart operators don't keep them after it expires.
I worked for Hobart for seven years, and I always did everything I could for the customer while I was onsite. And yes I've changed many ballast. Replaced ceiling tiles, replaced T&S valve cartridges, one time I even replaced the heater in the lobby of a Ruby Tuesday. Many hobart offices are independently owned, and different "owners" have different priorities on what they are willing to do at a restaurant.