The price of the Maintenance Cartridges, containing 4 uses, may seem high at first. From my experience I highly urge there use because of the following.
1) My job is to maintain industrial robots, including regular cleaning, inspection and repair. Even with my expertise, tools and professional cleaners I CANNOT achieve the cleaning/maintenance accomplished by the Maintenance Cartridge cycle.
2) Considering that at minimum wage it takes 5 hours to pay for a years worth of maintenance & deep cleanings. This figure factored in average taxes, cartridge, water, power and shipping costs. It takes me on average 6 hours a year to clean the 120 manually. You decide where your time is better spent! The total cost is less if purchase a bundle with the Maintenance Cartridge.
The maintenance cycle takes considerably longer than the cleaning cycle. I run it while my cats are sleeping. Since, I adopted this tactic I haven't had any accidents or kitties impatiently waiting for the CatGenie to finish.
My setup: CatGenie model 120 using softened water with 2 cats and cat activation setting engaged. Average lifespan of SaniSolution cartridge is 42 days. I thereby run a maintenance cycle for every 2 SaniSolution cartridge changes.