Quick take
Treat published intervals as starting points, then adjust for feed-water quality, usage and actual system performance.
Sediment prefilter
Typical replacement is around 6–12 months. Heavy sediment can shorten that dramatically.
Carbon prefilter
Typical replacement is also around 6–12 months. Carbon protects the membrane from disinfectants and can affect taste.
RO membrane
Many residential membranes last roughly 18–36 months, but feed chemistry, pressure and pretreatment can move that range significantly.
Post-carbon and remineralization
These are commonly changed around 6–12 months depending on design. Brand-specific proprietary systems should follow the exact cartridge schedule.