I have a Bernina 1230, and it must be ten years at least since I took it in for cleaning/oiling. The last time I took it in I noticed that the tech had not changed the tension from my setting to the factory default setting, which made me wonder if he actually checked anything. The machine was pretty clean, was not giving me problems, yet it cost well over $100 for what might have been nothing. That's when I decided to simply be consistent about cleaning and oiling the bobbin shuttle race (new machines don't have all those oil points that are on vintage machines). The machine has not given me a single problem in these ten years, which means I've saved over $1,000.
Honestly, I think the yearly maintenance thing is really unnecessary unless perhaps you use your machine professionally and sew on it for 8 hours a day.
Oh, and my car has over 250,000 miles on it.
Runs like a top.