Most need some sort of ongoing maint. If you get a typical CD ozone system, you have a chip to replace once every 9000 hours of operation. The HotSpring Freshwater III is an exception to this rule - nothing to do to it for ten years or so.
If you go with an Ionizer, you have electrodes or plates to replace, and the length of time varies from maker to maker, and water conditions effect this as well.
Have you ruled out a simple Dichlor regimen?
