There are three different types of filters available, each of which has its own unique advantages.
How often your spa filter cartridge needs replacing is dependant on a number of factors; the size of the filter, how often it’s cleaned, how much the spa is used and how much debris gets into the water. Generally a filter needs to be replaced every one or two years, or if you notice any of the following; either of the plastic ends are cracked, fabric pleats separating from the plastic ends or cleaning it doesn’t appear to get it any cleaner.
How often the filter needs to be cleaned also depends on the size of the filter, how much the spa is used and how much debris gets into the water. Generally portable or self contained spas should have their filters cleaned once a month. The best way to clean them is to blast them with a hose fitted with a high pressure nosel (some people clean their filters at a local self serve car wash). Don’t use any cleaning products not especially designed for cleaning filter cartridges.