It’s difficult to estimate how often the filter cartridge needs to be replaced because it depends not just on how much you use it but on the material you use. Hardwoods aren’t very taxing but plywood might be, depending entirely on the glue (which is usually hard to figure out). It’s just going to vary a great deal, with light users pushing past a year between changes, and heavy users who are cutting nonstop turning them over as often as every month or so. We’re working on filter pricing, but we expect it’s going to come in under $250.