Ann, I, too, have to use the machine to do the work, as my shoulder doesn’t like it otherwise. My KA mixer is circa 1980s, meaning the guts are most probably metal, not plastic or nylon. I do 2-l0af batches, two batches in one day. It does warm up some, but since I mix about 10 – 15 minutes at a time for each addition (hydrated flour, yeast, salt, porridge) and have time (~1/2 hr) between batches, it cools down. Sometimes the first mix takes longer, but since I am tearing the hydrated flour into Pecan-sized pieces, the mixer isn’t working so hard.