This based on my experience with my 1036 which is the only machine that I owned for over 30 years. I am in the habit of brushing out the bobbin area when I change bobbins but when I notice a difference in performance, it's time for a good cleaning. Usually I can tell by sound it's time to take things apart. If I do a good cleaning the lint out of the bobbin area both top and bottom and the feed dogs and oil & lube, she runs much smoother.