I have machines from 1918, 1926, 1929, 1949, 1952, 1955, 1956 and 1973 still going strong. The 1973 Elna 62C has a nylon gear that if it becomes lopsided from non use will end its usefulness. I just use mine regularly and so far so good. The others are all metal and I expect they will outlast me. I have had to replace a few belts, a few bobbin winder wheels and a tension spring on one Singer 301.