I just googled sewing machine needles, how often to change, etc. There is a lot of info. out there at the click of your mouse. I checked Sew Mama Sew, Schmetz needles web site (several good pics), and Threads Magazine - an article called "Preventive Sewing Machine Maintenance." One web site said to change the needle every 4 hours! When I attended the new owner's class after I bought my H. Viking Opal 670, they said to change the needle every 5-7 hrs. A damaged needle can be responsible for skipped stitches and tearing fabrics. I would guess most people probably don't change their needles often enough. Probably don't clean the bobbin area often enough either. Good preventive maintenance makes all the difference in the world in keeping one's machine in tip-top shape. JCY