I took a class at the Bernina dealership, and the instructor stated that the Bernina's should be oiled every 8 hours. One of the ladies in the class pulled out a yellowish crusty bag, and said, "Is this the oil?" i.e. most of the women didn't know to oil that frequently. I know that before my Juki, I was totally negligent in oiling machines. The expression,"Nothing runs like a well-oiled machine" is true in sewing also. If you look at the guts of a machine the needle bar goes up and down, and it only makes sense to have it oiled often to reduce friction.
Please ask your Bernina dealership, or service repairman. You might be surprised.