Thanks for putting that together Sfish! Very helpful.
In general, ro membranes need to be changed when the output flow(permeate) slows down. If you replace the carbon prefilters every 6-12 months, membranes last a long time.
As others have said, di needs changed since your tds is not 0.
BTW, are you on your own well or city water? If city, do they treat with chlorine?
BTW, are you on your own well or city water? If city, do they treat with chlorine?