Heavy dust will kill so fast. However, in a 30 x 18 cm room, the filter lasted about 6 months (about 2 furniture projects and 2 kitchen cabinet assemblies that took 3 months). On a positive note, if you get one, you can use the template sleeve to create your own new FPR 10 rated big box air filter if you like. I've done it and I just keep replacing the innards as it fills up. That alone is worth the cost of a filter to me.