What your feed water does to filter life
Both parts have a set replacement interval. Hard incoming water is what wears them out before it.
Two parts are consumable: the combo cartridge, which holds the sediment and carbon stages, and the RO membrane itself, which does the actual separation.
Total dissolved solids (TDS) in the incoming water are what load the cartridge and foul the membrane, so a hard-water site may need both changed before their interval is up. The maximum feed TDS is 800 ppm; above it, the system is operating outside its specification.
Two things upstream matter as much
Free chlorine damages the membrane and has to be removed before the water reaches it. That is part of what the carbon stage is for. Feed temperature matters too: output falls as the water gets colder, and the system must never be allowed to freeze.
On the under-sink platform the replacement parts are LXL-A0002 for the cartridge and LXL-A0001 for the membrane. Commercial models take different parts, so contact us to confirm the correct one before ordering rather than matching on service life alone.