I only do piecing on my DMS. I wind a dozen bobbins at a time. When I do that, I also clean my machine, and change my needle. It's just a habit I'm in, and keeps everything running smoothly. Needles aren't really all that expensive, and well worth having a good sharp one in place. It helps stop skipped stitches as well, so in the long run that saves time, which is worth more to me that saving a few pennies on needles. (I save old empty pill bottles to put the used ones in so I can dispose of them safely.)