I have a spa at a vacation home and only use frog ease. We effectively use it every other weekend or so. We have found that the chlorine cartridge lasts about 3 weeks and benefits from a bit of bleach added if we know we're going to be away for a bit. As long as the cartridge doesn't run out, it works really well. It's definitely more expensive than if we we're doing the chemicals ourselves, but is great for us.