We've had customers that have gotten well over a year out of a system but that not the norm. I'd say under average usage to expect about 4-5 months out of a unit. It's been stated on here many times but for the benefit of 'newbies' it bears repeating: Sleep on a satin or silk pillow case--not cotton. Cotton does two things to a unit. #1. Cotton 'wicks' the hair and dries it out causing the hair to break and look dull. #2. Cotton 'hooks' the hair and pulls on it causing breakage. Going with a silk or satin pillow cause avoids these issues. Also, use a charcoal shower filter to 'soften' the water and remove chemicals that are hard on the hair (and your skin). And of course, use Back 2 Natural blender/conditioner to revive color and shine.
Regards,
John