Berninas have a 25 year warranty. They should have a check up every year, just as you get cars tuned up. There are some really old Bernina's out there chugging right along. They are work horses. I have seen the same model as mine sew animal pelts together without even a sigh. That being said, I think it is a good idea to have a back up machine for the times yours is having her checkup. Or you can do what I am going to do, schedule service while I am taking a class. They will loan me one to do the class on and mine will be ready to go home when the class is over.
I do embroidery with my Bernina, so my hubby decided I needed a little machine to use while Nina is creating, so he got me a little Brother (no bells or whistles), it is nice and works as a secondary, but it definitely isn't my Bernina.