I am not the quarterback, I am the coach and if you wanna play you had better perform.
I can say with all honesty that if a service man in my company spent 3 hours trouble shooting a fart fan, there had better be a damn good reason or I would be looking for a new service man.
Put yourself in the customers shoes, would you pay a 3 hour ticket for nothing?
i tend to differentiate between a 3 hr call where the service guy says "I can't find the problem, I'm leaving, here's your bill" and one where the customer says "that's it...no more"
who's to say, he wouldn't have found it in 15 mins and fixed it?