You've not noticed it with the Singers? I can only sew about 45 mn constant before they heat up too much for my foot. (I sew in stockings). But I am talking near constant sewing, like FMQ or satin stitching yards of ribbon on. That is why I had DH swap out the Singer for a new type on my 15, and why I have a different setup for my White (came with the same type).