I"ve heard warnings that this saw goes through bearings, belts and other parts fast. If I'm sawing no more than , say 3 hours per week with it, and I'm careful about cleaning etc., what kind of parts will I need to replace per year?

It can be difficult to say. It will depend on the type of material, thickness and length. We recommended cleaning the saw regularly to keep bits of glass and debris out of the grommets and belt which will help keep the parts lasting longer. In general, for light duty use you should expect replacement of the belt every 6 months and the grommets every 6 to 9 months.