In my opinion, it's not just changing out the turbo that's important, is cleaning the tubes, changing the orings, and replacing the mirrors.
It's taking care of the laser to ensure that it runs consistently day in and day out.
I have at least 30 machines that I take care of with over 50,000 hours. Very rarely do I have "break downs" or unscheduled service calls. It's just a matter of doing all the service when it's recommended.
Yes, I do make money on service, Yes, I do make money changing out turbos. And, Yes, I have a lot of very old machines that still make tons of money.