I love your Guardsman, but that poor Sanitaire sounds like it really needs a new belt. When I was little we had a Eureka Express canister and I only remember my mother changing the belt once. After that we had several Electrolux machines, which never require you to change the belt. However after having several Kirbys I change the belt in them religiously ever 6 months. When I change the belt I put the 6 month mark on the calendar in my BlackBerry so I make sure to change it. My Diamond and Ultimate G have belts that should last a lot longer than a Sanitaire or Convertible style Hoover belt, but the minimal cost is far outweighed by the better preformace. My suggestion is to buy the largest pack of Sanitaire belts you can find and change it every few months. Its a wonderful vacuum that you have, and a new belt should keep it cleaning at its best. I know those machines are a real beast and can out clean and out last many others on the market today.