I have an old, old, Bernina 830. I bought it new, about 25 years ago. It has never once jammed or knotted up the thread. It has gone through 3 foot pedals. I used to sew curtains, etc. professionally. I have had it cleaned once a year every year and that is all the maintenance it has had. Last year I traded my Bernina 135 in on a new 730. It too is wonderful. Harder to get used to because it too does so much. But I really love my Berninas.